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• How do I prevent a C# method from executing using an attribute validator?

  - by Boydski

  I'd like to create an attribute-based validator that goes a few steps beyond what I've seen in examples. It'll basically prevent methods or other functionality from executing. Please be aware that I'm having to use AzMan since I have no availability to Active Directory in this scenario. Here's some pseudo code of what what I'm looking for: // Attribute validator class AttributeUsage is arbitrary at this point and may include other items [AttributeUsage( AttributeTargets.Method | AttributeTargets.Property, AllowMultiple = true, Inherited = true )] public class PermissionsValidatorAttribute : Attribute { public PermissionsValidatorAttribute(PermissionEnumeration permission){...} public bool UserCanCreateAndEdit(){...} public bool UserCanDelete(){...} public bool UserCanUpload(){...} } Here's a sample of a class/member that'll be decorated. The method will not be executed at all if the PermissionValidator.UserCanDelete() doesn't return true from wherever it's executed: public class DoStuffNeedingPermissions { [PermissionValidator(PermissionEnumeration.MustHaveDeletePermission)] public void DeleteSomething(){...} } I know this is a simple, incomplete example. But you should get the gist of what I'm needing. Make the assumption that DeleteSomething() already exists and I'm preferring to NOT modify the code within the method at all. I'm currently looking at things like the Validation Application Block and am messing with custom attribute POC's. But I'd love to hear opinions with code samples from everyone out there. I'm also certainly not opposed to other methods of accomplishing the same thing such as extension methods or whatever may work to accomplish the same thing. Please remember I'm making the attempt to minimize changes to existing DoStuffNeedingPermissions code. Thanks everyone!

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• N-tier Repository POCOs - Aggregates?

  - by Sam

  Assume the following simple POCOs, Country and State: public partial class Country { public Country() { States = new List<State>(); } public virtual int CountryId { get; set; } public virtual string Name { get; set; } public virtual string CountryCode { get; set; } public virtual ICollection<State> States { get; set; } } public partial class State { public virtual int StateId { get; set; } public virtual int CountryId { get; set; } public virtual Country Country { get; set; } public virtual string Name { get; set; } public virtual string Abbreviation { get; set; } } Now assume I have a simple respository that looks something like this: public partial class CountryRepository : IDisposable { protected internal IDatabase _db; public CountryRepository() { _db = new Database(System.Configuration.ConfigurationManager.AppSettings["DbConnName"]); } public IEnumerable<Country> GetAll() { return _db.Query<Country>("SELECT * FROM Countries ORDER BY Name", null); } public Country Get(object id) { return _db.SingleById(id); } public void Add(Country c) { _db.Insert(c); } /* ...And So On... */ } Typically in my UI I do not display all of the children (states), but I do display an aggregate count. So my country list view model might look like this: public partial class CountryListVM { [Key] public int CountryId { get; set; } public string Name { get; set; } public string CountryCode { get; set; } public int StateCount { get; set; } } When I'm using the underlying data provider (Entity Framework, NHibernate, PetaPoco, etc) directly in my UI layer, I can easily do something like this: IList<CountryListVM> list = db.Countries .OrderBy(c => c.Name) .Select(c => new CountryListVM() { CountryId = c.CountryId, Name = c.Name, CountryCode = c.CountryCode, StateCount = c.States.Count }) .ToList(); But when I'm using a repository or service pattern, I abstract away direct access to the data layer. It seems as though my options are to: Return the Country with a populated States collection, then map over in the UI layer. The downside to this approach is that I'm returning a lot more data than is actually needed. -or- Put all my view models into my Common dll library (as opposed to having them in the Models directory in my MVC app) and expand my repository to return specific view models instead of just the domain pocos. The downside to this approach is that I'm leaking UI specific stuff (MVC data validation annotations) into my previously clean POCOs. -or- Are there other options? How are you handling these types of things?

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• Hibernate many-to-many mapping not saved in pivot table

  - by vincent

  I having problems saving many to many relationships to a pivot table. The way the pojos are created is unfortunately a pretty long process which spans over a couple of different threads which work on the (to this point un-saved) object until it is finally persisted. I associate the related objects to one another right after they are created and when debugging I can see the List of related object populated with their respective objects. So basically all is fine to this point. When I persist the object everything get saved except the relations in the pivot table. mapping files: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.thebeansgroup.jwinston.plugin.orm.hibernate.object"> <class name="ShowObject" table="show_object"> <id name="id"> <generator class="native" /> </id> <property name="name" /> <set cascade="all" inverse="true" name="venues" table="venue_show"> <key column="show_id"/> <many-to-many class="VenueObject"/> </set> </class> </hibernate-mapping> and the other <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.thebeansgroup.jwinston.plugin.orm.hibernate.object"> <class name="VenueObject" table="venue_object"> <id name="id"> <generator class="native"/> </id> <property name="name"/> <property name="latitude" type="integer"/> <property name="longitude" type="integer"/> <set cascade="all" inverse="true" name="shows" table="venue_show"> <key column="venue_id"/> <many-to-many class="ShowObject"/> </set> </class> </hibernate-mapping> pojos: public class ShowObject extends OrmObject { private Long id; private String name; private Set venues; public ShowObject() { } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set getVenues() { return venues; } public void setVenues(Set venues) { this.venues = venues; } } and the other: public class VenueObject extends OrmObject { private Long id; private String name; private int latitude; private int longitude; private Set shows = new HashSet(); public VenueObject() { } @Id @GeneratedValue(strategy = GenerationType.AUTO) public Long getId() { return id; } public void setId(Long id) { this.id = id; } public int getLatitude() { return latitude; } public void setLatitude(int latitude) { this.latitude = latitude; } public int getLongitude() { return longitude; } public void setLongitude(int longitude) { this.longitude = longitude; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set getShows() { return shows; } public void setShows(Set shows) { this.shows = shows; } } Might the problem be related to the lack of annotations?

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• Why is there a constructor method if you can assign the values to variables?

  - by Joel

  I'm just learning PHP, and I'm confused about what the purpose of the __construct() method? If I can do this: class Bear { // define properties public $name = 'Bill'; public $weight = 200; // define methods public function eat($units) { echo $this->name." is eating ".$units." units of food... <br />"; $this->weight += $units; } } Then why do it with a constructor instead? : class Bear { // define properties public $name; public $weight; public function __construct(){ $this->name = 'Bill'; $this->weight = 200; } // define methods public function eat($units) { echo $this->name." is eating ".$units." units of food... <br />"; $this->weight += $units; } }

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• Is it safe to assert a functions return type?

  - by wb

  This question is related to this question. I have several models stored in a collection. I loop through the collection and validate each field. Based on the input, a field can either be successful, have an error or a warning. Is it safe to unit test each decorator and assert that the type of object returned is what you would expect based on the given input? I could perhaps see this being an issue for a language with function return types since my validation function can return one of 3 types. This is the code I'm fiddling with: <!-- #include file = "../lib/Collection.asp" --> <style type="text/css"> td { padding: 4px; } td.error { background: #F00F00; } td.warning { background: #FC0; } </style> <% Class UserModel Private m_Name Private m_Age Private m_Height Public Property Let Name(value) m_Name = value End Property Public Property Get Name() Name = m_Name End Property Public Property Let Age(value) m_Age = value End Property Public Property Get Age() Age = m_Age End Property Public Property Let Height(value) m_Height = value End Property Public Property Get Height() Height = m_Height End Property End Class Class NameValidation Private m_Name Public Function Init(name) m_Name = name End Function Public Function Validate() Dim validationObject If Len(m_Name) < 5 Then Set validationObject = New ValidationError Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Name Set Validate = validationObject End Function End Class Class AgeValidation Private m_Age Public Function Init(age) m_Age = age End Function Public Function Validate() Dim validationObject If m_Age < 18 Then Set validationObject = New ValidationError ElseIf m_Age = 18 Then Set validationObject = New ValidationWarning Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Age Set Validate = validationObject End Function End Class Class HeightValidation Private m_Height Public Function Init(height) m_Height = height End Function Public Function Validate() Dim validationObject If m_Height > 400 Then Set validationObject = New ValidationError ElseIf m_Height = 324 Then Set validationObject = New ValidationWarning Else Set validationObject = New ValidationSuccess End If validationObject.CellValue = m_Height Set Validate = validationObject End Function End Class Class ValidationError Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "error" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ValidationWarning Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "warning" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ValidationSuccess Private m_CSSClass Private m_CellValue Public Property Get CSSClass() CSSClass = "" End Property Public Property Let CellValue(value) m_CellValue = value End Property Public Property Get CellValue() CellValue = m_CellValue End Property End Class Class ModelValidator Public Function ValidateModel(model) Dim modelValidation : Set modelValidation = New CollectionClass ' Validate name Dim name : Set name = New NameValidation name.Init model.Name modelValidation.Add name ' Validate age Dim age : Set age = New AgeValidation age.Init model.Age modelValidation.Add age ' Validate height Dim height : Set height = New HeightValidation height.Init model.Height modelValidation.Add height Dim validatedProperties : Set validatedProperties = New CollectionClass Dim modelVal For Each modelVal In modelValidation.Items() validatedProperties.Add modelVal.Validate() Next Set ValidateModel = validatedProperties End Function End Class Dim modelCollection : Set modelCollection = New CollectionClass Dim user1 : Set user1 = New UserModel user1.Name = "Mike" user1.Age = 12 user1.Height = 32 modelCollection.Add user1 Dim user2 : Set user2 = New UserModel user2.Name = "Phil" user2.Age = 18 user2.Height = 432 modelCollection.Add user2 Dim user3 : Set user3 = New UserModel user3.Name = "Michele" user3.Age = 32 user3.Height = 324 modelCollection.Add user3 ' Validate all models in the collection Dim modelValue Dim validatedModels : Set validatedModels = New CollectionClass For Each modelValue In modelCollection.Items() Dim objModelValidator : Set objModelValidator = New ModelValidator validatedModels.Add objModelValidator.ValidateModel(modelValue) Next %> <table> <tr> <td>Name</td> <td>Age</td> <td>Height</td> </tr> <% Dim r, c For Each r In validatedModels.Items() %><tr><% For Each c In r.Items() %><td class="<%= c.CSSClass %>"><%= c.CellValue %></td><% Next %></tr><% Next %> </table> Thank you.

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• How to send KeyEvents through an input method service to a Dialog, or a Spinner menu?

  - by shutdown11

  I'm trying to implement an input method service that receives intents sent by a remote client, and in response to those sends an appropriate KeyEvent. I'm using in the input method service this method private void keyDownUp(int keyEventCode) { getCurrentInputConnection().sendKeyEvent( new KeyEvent(KeyEvent.ACTION_DOWN, keyEventCode)); getCurrentInputConnection().sendKeyEvent( new KeyEvent(KeyEvent.ACTION_UP, keyEventCode)); } to send KeyEvents as in the Simple Sofykeyboard Sample, and it works in the home, in Activities... but it doesn't works when a Dialog or the menu of a Spinner is in foreground. The events is sent to the parent activity behind the Dialog. Is there any way to send keys and control the device like using the hardware keys from an input method? Better explanation on what I'm trying to do: I am kind of writng an Input Method that allows to control the device from remote. I write in a client (a java application on my desktop pc) a command (for example "UP"), a server on the device with sendBroadcast() sends the intent with the information, and a receiver in the input method gets it and call keyDownUp with the keycode of the DPAD_UP key. It generally works, but when I go to an app that shows a dialog, the keyDownUp method don't sends the key event to the dialog, for example for select the yes or not buttons, but it keeps to control the activty behind the Dialog.

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• How to force my method to accept objects from external software?

  - by Roman

  I have a method which needs to take a callback object as an argument and then (at the moment when it's needed) my method will call a specific method of the callback object. I wrote a class called Manager which has a method called addListener. As the argument for this method I need to use a callback object which is defined by the external software. So, I define the addListener in the following way: public void addListener(Listener listener). Of course Eclipse complains because it does not know what Listener is (because the Listener is defined by the external software). The only think that I know (should know) about the Listener is that it has a method called doSomething. So, to pleasure Eclipse I add an interface before my Manager class: interface Listener { void doSomething(); } public class CTManager { ... The problem seems to be solved but then I try to test my software. So, I create a class called test. In this class I create an instance of the Manager class and try to use addListener method of this instance. I also create a class Listener, instantiate it and give the instance to the addListener. And it's the place where the problem appears. Eclipse writes that addListener is not applicable to the given argument. I think it's because it expect something from my Listenr interface but gets something from the Listener class. How can I solve this problem?

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• EF Code First to SQL Azure

  - by Predrag Pejic

  I am using EF Code First to create a database on local .\SQLEXPRESS. Among others. I have these 2 classes: public class Shop { public int ShopID { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a name!")] [MaxLength(25, ErrorMessage = "Name must be 25 characters or less")] public string Name { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter an address!")] [MaxLength(30, ErrorMessage = "Address must be 30 characters or less")] public string Address { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a valid city name!")] [MaxLength(30, ErrorMessage = "City name must be 30 characters or less")] public string City { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a phone number!")] [MaxLength(14, ErrorMessage = "Phone number must be 14 characters or less")] public string Phone { get; set; } [MaxLength(100, ErrorMessage = "Description must be 50 characters or less")] public string Description { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a WorkTime!")] public DateTime WorkTimeBegin { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a WorkTime!")] public DateTime WorkTimeEnd { get; set; } public DateTime? SaturdayWorkTimeBegin { get; set; } public DateTime? SaturdayWorkTimeEnd { get; set; } public DateTime? SundayWorkTimeBegin { get; set; } public DateTime? SundayWorkTimeEnd { get; set; } public int ShoppingPlaceID { get; set; } public virtual ShoppingPlace ShoppingPlace { get; set; } public virtual ICollection<Category> Categories { get; set; } } public class ShoppingPlace { [Key] public int ShopingplaceID { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a name!")] [MaxLength(25, ErrorMessage = "Name must be 25 characters or less")] public string Name { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter an address!")] [MaxLength(50, ErrorMessage = "Address must be 50 characters or less")] public string Address { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a city name!")] [MaxLength(30, ErrorMessage = "City must be 30 characters or less")] public string City { get; set; } [Required(AllowEmptyStrings = false, ErrorMessage = "You must enter a valid phone number!")] [MaxLength(14, ErrorMessage = "Phone number must be 14 characters or less")] public string Phone { get; set; } public int ShoppingCenterID { get; set; } public virtual ShoppingCenter ShoppingCenter { get; set; } public virtual ICollection<Shop> Shops { get; set; } } and a method in DbContext: modelBuilder.Entity<Item>() .HasRequired(p => p.Category) .WithMany(a => a.Items) .HasForeignKey(a => a.CategoryID) .WillCascadeOnDelete(false); modelBuilder.Entity<Category>() .HasRequired(a => a.Shop) .WithMany(a => a.Categories) .HasForeignKey(a => a.ShopID) .WillCascadeOnDelete(false); modelBuilder.Entity<Shop>() .HasOptional(a => a.ShoppingPlace) .WithMany(a => a.Shops) .HasForeignKey(a => a.ShoppingPlaceID) .WillCascadeOnDelete(false); modelBuilder.Entity<ShoppingPlace>() .HasOptional(a => a.ShoppingCenter) .WithMany(a => a.ShoppingPlaces) .HasForeignKey(a => a.ShoppingCenterID) .WillCascadeOnDelete(false); Why I can't create Shop without creating and populating ShopingPlace. How to achieve that? EDIT: Tried with: modelBuilder.Entity<Shop>() .HasOptional(a => a.ShoppingPlace) .WithOptionalPrincipal(); modelBuilder.Entity<ShoppingPlace>() .HasOptional(a => a.ShoppingCenter) .WithOptionalPrincipal(); and it passed, but what is the difference? And why in SQL Server i am allowed to see ShoppingPlaceID and ShoppingPlace_ShopingPlaceID when in the case of Item and Category i see only one?

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• Overriding GetHashCode in a mutable struct - What NOT to do?

  - by Kyle Baran

  I am using the XNA Framework to make a learning project. It has a Point struct which exposes an X and Y value; for the purpose of optimization, it breaks the rules for proper struct design, since its a mutable struct. As Marc Gravell, John Skeet, and Eric Lippert point out in their respective posts about GetHashCode() (which Point overrides), this is a rather bad thing, since if an object's values change while its contained in a hashmap (ie, LINQ queries), it can become "lost". However, I am making my own Point3D struct, following the design of Point as a guideline. Thus, it too is a mutable struct which overrides GetHashCode(). The only difference is that mine exposes and int for X, Y, and Z values, but is fundamentally the same. The signatures are below: public struct Point3D : IEquatable<Point3D> { public int X; public int Y; public int Z; public static bool operator !=(Point3D a, Point3D b) { } public static bool operator ==(Point3D a, Point3D b) { } public Point3D Zero { get; } public override int GetHashCode() { } public override bool Equals(object obj) { } public bool Equals(Point3D other) { } public override string ToString() { } } I have tried to break my struct in the way they describe, namely by storing it in a List<Point3D>, as well as changing the value via a method using ref, but I did not encounter they behavior they warn about (maybe a pointer might allow me to break it?). Am I being too cautious in my approach, or should I be okay to use it as is?

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• Unity – Part 5: Injecting Values

  - by Ricardo Peres

  Introduction This is the fifth post on Unity. You can find the introductory post here, the second post, on dependency injection here, a third one on Aspect Oriented Programming (AOP) here and the latest so far, on writing custom extensions, here. This time we will talk about injecting simple values. An Inversion of Control (IoC) / Dependency Injector (DI) container like Unity can be used for things other than injecting complex class dependencies. It can also be used for setting property values or method/constructor parameters whenever a class is built. The main difference is that these values do not have a lifetime manager associated with them and do not come from the regular IoC registration store. Unlike, for instance, MEF, Unity won’t let you register as a dependency a string or an integer, so you have to take a different approach, which I will describe in this post. Scenario Let’s imagine we have a base interface that describes a logger – the same as in previous examples: 1: public interface ILogger 2: { 3: void Log(String message); 4: } And a concrete implementation that writes to a file: 1: public class FileLogger : ILogger 2: { 3: public String Filename 4: { 5: get; 6: set; 7: } 8:  9: #region ILogger Members 10:  11: public void Log(String message) 12: { 13: using (Stream file = File.OpenWrite(this.Filename)) 14: { 15: Byte[] data = Encoding.Default.GetBytes(message); 16: 17: file.Write(data, 0, data.Length); 18: } 19: } 20:  21: #endregion 22: } And let’s say we want the Filename property to come from the application settings (appSettings) section on the Web/App.config file. As usual with Unity, there is an extensibility point that allows us to automatically do this, both with code configuration or statically on the configuration file. Extending Injection We start by implementing a class that will retrieve a value from the appSettings by inheriting from ValueElement: 1: sealed class AppSettingsParameterValueElement : ValueElement, IDependencyResolverPolicy 2: { 3: #region Private methods 4: private Object CreateInstance(Type parameterType) 5: { 6: Object configurationValue = ConfigurationManager.AppSettings[this.AppSettingsKey]; 7:  8: if (parameterType != typeof(String)) 9: { 10: TypeConverter typeConverter = this.GetTypeConverter(parameterType); 11:  12: configurationValue = typeConverter.ConvertFromInvariantString(configurationValue as String); 13: } 14:  15: return (configurationValue); 16: } 17: #endregion 18:  19: #region Private methods 20: private TypeConverter GetTypeConverter(Type parameterType) 21: { 22: if (String.IsNullOrEmpty(this.TypeConverterTypeName) == false) 23: { 24: return (Activator.CreateInstance(TypeResolver.ResolveType(this.TypeConverterTypeName)) as TypeConverter); 25: } 26: else 27: { 28: return (TypeDescriptor.GetConverter(parameterType)); 29: } 30: } 31: #endregion 32:  33: #region Public override methods 34: public override InjectionParameterValue GetInjectionParameterValue(IUnityContainer container, Type parameterType) 35: { 36: Object value = this.CreateInstance(parameterType); 37: return (new InjectionParameter(parameterType, value)); 38: } 39: #endregion 40:  41: #region IDependencyResolverPolicy Members 42:  43: public Object Resolve(IBuilderContext context) 44: { 45: Type parameterType = null; 46:  47: if (context.CurrentOperation is ResolvingPropertyValueOperation) 48: { 49: ResolvingPropertyValueOperation op = (context.CurrentOperation as ResolvingPropertyValueOperation); 50: PropertyInfo prop = op.TypeBeingConstructed.GetProperty(op.PropertyName); 51: parameterType = prop.PropertyType; 52: } 53: else if (context.CurrentOperation is ConstructorArgumentResolveOperation) 54: { 55: ConstructorArgumentResolveOperation op = (context.CurrentOperation as ConstructorArgumentResolveOperation); 56: String args = op.ConstructorSignature.Split('(')[1].Split(')')[0]; 57: Type[] types = args.Split(',').Select(a => Type.GetType(a.Split(' ')[0])).ToArray(); 58: ConstructorInfo ctor = op.TypeBeingConstructed.GetConstructor(types); 59: parameterType = ctor.GetParameters().Where(p => p.Name == op.ParameterName).Single().ParameterType; 60: } 61: else if (context.CurrentOperation is MethodArgumentResolveOperation) 62: { 63: MethodArgumentResolveOperation op = (context.CurrentOperation as MethodArgumentResolveOperation); 64: String methodName = op.MethodSignature.Split('(')[0].Split(' ')[1]; 65: String args = op.MethodSignature.Split('(')[1].Split(')')[0]; 66: Type[] types = args.Split(',').Select(a => Type.GetType(a.Split(' ')[0])).ToArray(); 67: MethodInfo method = op.TypeBeingConstructed.GetMethod(methodName, types); 68: parameterType = method.GetParameters().Where(p => p.Name == op.ParameterName).Single().ParameterType; 69: } 70:  71: return (this.CreateInstance(parameterType)); 72: } 73:  74: #endregion 75:  76: #region Public properties 77: [ConfigurationProperty("appSettingsKey", IsRequired = true)] 78: public String AppSettingsKey 79: { 80: get 81: { 82: return ((String)base["appSettingsKey"]); 83: } 84:  85: set 86: { 87: base["appSettingsKey"] = value; 88: } 89: } 90: #endregion 91: } As you can see from the implementation of the IDependencyResolverPolicy.Resolve method, this will work in three different scenarios: When it is applied to a property; When it is applied to a constructor parameter; When it is applied to an initialization method. The implementation will even try to convert the value to its declared destination, for example, if the destination property is an Int32, it will try to convert the appSettings stored string to an Int32. Injection By Configuration If we want to configure injection by configuration, we need to implement a custom section extension by inheriting from SectionExtension, and registering our custom element with the name “appSettings”: 1: sealed class AppSettingsParameterInjectionElementExtension : SectionExtension 2: { 3: public override void AddExtensions(SectionExtensionContext context) 4: { 5: context.AddElement<AppSettingsParameterValueElement>("appSettings"); 6: } 7: } And on the configuration file, for setting a property, we use it like this: 1: <appSettings> 2: <add key="LoggerFilename" value="Log.txt"/> 3: </appSettings> 4: <unity xmlns="http://schemas.microsoft.com/practices/2010/unity"> 5: <container> 6: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.ConsoleLogger, MyAssembly"/> 7: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.FileLogger, MyAssembly" name="File"> 8: <lifetime type="singleton"/> 9: <property name="Filename"> 10: <appSettings appSettingsKey="LoggerFilename"/> 11: </property> 12: </register> 13: </container> 14: </unity> If we would like to inject the value as a constructor parameter, it would be instead: 1: <unity xmlns="http://schemas.microsoft.com/practices/2010/unity"> 2: <sectionExtension type="MyNamespace.AppSettingsParameterInjectionElementExtension, MyAssembly" /> 3: <container> 4: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.ConsoleLogger, MyAssembly"/> 5: <register type="MyNamespace.ILogger, MyAssembly" mapTo="MyNamespace.FileLogger, MyAssembly" name="File"> 6: <lifetime type="singleton"/> 7: <constructor> 8: <param name="filename" type="System.String"> 9: <appSettings appSettingsKey="LoggerFilename"/> 10: </param> 11: </constructor> 12: </register> 13: </container> 14: </unity> Notice the appSettings section, where we add a LoggerFilename entry, which is the same as the one referred by our AppSettingsParameterInjectionElementExtension extension. For more advanced behavior, you can add a TypeConverterName attribute to the appSettings declaration, where you can pass an assembly qualified name of a class that inherits from TypeConverter. This class will be responsible for converting the appSettings value to a destination type. Injection By Attribute If we would like to use attributes instead, we need to create a custom attribute by inheriting from DependencyResolutionAttribute: 1: [Serializable] 2: [AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property, AllowMultiple = false, Inherited = true)] 3: public sealed class AppSettingsDependencyResolutionAttribute : DependencyResolutionAttribute 4: { 5: public AppSettingsDependencyResolutionAttribute(String appSettingsKey) 6: { 7: this.AppSettingsKey = appSettingsKey; 8: } 9:  10: public String TypeConverterTypeName 11: { 12: get; 13: set; 14: } 15:  16: public String AppSettingsKey 17: { 18: get; 19: private set; 20: } 21:  22: public override IDependencyResolverPolicy CreateResolver(Type typeToResolve) 23: { 24: return (new AppSettingsParameterValueElement() { AppSettingsKey = this.AppSettingsKey, TypeConverterTypeName = this.TypeConverterTypeName }); 25: } 26: } As for file configuration, there is a mandatory property for setting the appSettings key and an optional TypeConverterName  for setting the name of a TypeConverter. Both the custom attribute and the custom section return an instance of the injector AppSettingsParameterValueElement that we implemented in the first place. Now, the attribute needs to be placed before the injected class’ Filename property: 1: public class FileLogger : ILogger 2: { 3: [AppSettingsDependencyResolution("LoggerFilename")] 4: public String Filename 5: { 6: get; 7: set; 8: } 9:  10: #region ILogger Members 11:  12: public void Log(String message) 13: { 14: using (Stream file = File.OpenWrite(this.Filename)) 15: { 16: Byte[] data = Encoding.Default.GetBytes(message); 17: 18: file.Write(data, 0, data.Length); 19: } 20: } 21:  22: #endregion 23: } Or, if we wanted to use constructor injection: 1: public class FileLogger : ILogger 2: { 3: public String Filename 4: { 5: get; 6: set; 7: } 8:  9: public FileLogger([AppSettingsDependencyResolution("LoggerFilename")] String filename) 10: { 11: this.Filename = filename; 12: } 13:  14: #region ILogger Members 15:  16: public void Log(String message) 17: { 18: using (Stream file = File.OpenWrite(this.Filename)) 19: { 20: Byte[] data = Encoding.Default.GetBytes(message); 21: 22: file.Write(data, 0, data.Length); 23: } 24: } 25:  26: #endregion 27: } Usage Just do: 1: ILogger logger = ServiceLocator.Current.GetInstance<ILogger>("File"); And off you go! A simple way do avoid hardcoded values in component registrations. Of course, this same concept can be applied to registry keys, environment values, XML attributes, etc, etc, just change the implementation of the AppSettingsParameterValueElement class. Next stop: custom lifetime managers.

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• LazyInitializationException when adding to a list that is held within a entity class using hibernate

  - by molleman

  Right so i am working with hibernate gilead and gwt to persist my data on users and files of a website. my users have a list of file locations. i am using annotations to map my classes to the database. i am getting a org.hibernate.LazyInitializationException when i try to add file locations to the list that is held in the user class. this is a method below that is overridden from a external file upload servlet class that i am using. when the file uploads it calls this method. the user1 is loaded from the database elsewhere. the exception occurs at user1.getFileLocations().add(fileLocation); . i dont understand it really at all.! any help would be great. the stack trace of the error is below public String executeAction(HttpServletRequest request, List<FileItem> sessionFiles) throws UploadActionException { for (FileItem item : sessionFiles) { if (false == item.isFormField()) { try { YFUser user1 = (YFUser)getSession().getAttribute(SESSION_USER); // This is the location where a file will be stored String fileLocationString = "/Users/Stefano/Desktop/UploadedFiles/" + user1.getUsername(); File fl = new File(fileLocationString); fl.mkdir(); // so here i will create the a file container for my uploaded file File file = File.createTempFile("upload-", ".bin",fl); // this is where the file is written to disk item.write(file); // the FileLocation object is then created FileLocation fileLocation = new FileLocation(); fileLocation.setLocation(fileLocationString); //test System.out.println("file path = "+file.getPath()); user1.getFileLocations().add(fileLocation); //the line above is where the exception occurs } catch (Exception e) { throw new UploadActionException(e.getMessage()); } } removeSessionFileItems(request); } return null; } //This is the class file for a Your Files User @Entity @Table(name = "yf_user_table") public class YFUser implements Serializable,ILightEntity { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "user_id",nullable = false) private int userId; @Column(name = "username") private String username; @Column(name = "password") private String password; @Column(name = "email") private String email; @ManyToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_FILELOCATION", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "locationId") }) private List<FileLocation> fileLocations = new ArrayList<FileLocation>() ; public YFUser(){ } public int getUserId() { return userId; } private void setUserId(int userId) { this.userId = userId; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public List<FileLocation> getFileLocations() { if(fileLocations ==null){ fileLocations = new ArrayList<FileLocation>(); } return fileLocations; } public void setFileLocations(List<FileLocation> fileLocations) { this.fileLocations = fileLocations; } /* public void addFileLocation(FileLocation location){ fileLocations.add(location); }*/ @Override public void addProxyInformation(String property, Object proxyInfo) { // TODO Auto-generated method stub } @Override public String getDebugString() { // TODO Auto-generated method stub return null; } @Override public Object getProxyInformation(String property) { // TODO Auto-generated method stub return null; } @Override public boolean isInitialized(String property) { // TODO Auto-generated method stub return false; } @Override public void removeProxyInformation(String property) { // TODO Auto-generated method stub } @Override public void setInitialized(String property, boolean initialised) { // TODO Auto-generated method stub } @Override public Object getValue() { // TODO Auto-generated method stub return null; } } @Entity @Table(name = "fileLocationTable") public class FileLocation implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "locationId", updatable = false, nullable = false) private int ieId; @Column (name = "location") private String location; public FileLocation(){ } public int getIeId() { return ieId; } private void setIeId(int ieId) { this.ieId = ieId; } public String getLocation() { return location; } public void setLocation(String location) { this.location = location; } } Apr 2, 2010 11:33:12 PM org.hibernate.LazyInitializationException <init> SEVERE: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365) at org.hibernate.collection.AbstractPersistentCollection.write(AbstractPersistentCollection.java:205) at org.hibernate.collection.PersistentBag.add(PersistentBag.java:297) at com.example.server.TestServiceImpl.saveFileLocation(TestServiceImpl.java:132) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at net.sf.gilead.gwt.PersistentRemoteService.processCall(PersistentRemoteService.java:174) at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62) at javax.servlet.http.HttpServlet.service(HttpServlet.java:713) at javax.servlet.http.HttpServlet.service(HttpServlet.java:806) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:396) at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488) Apr 2, 2010 11:33:12 PM net.sf.gilead.core.PersistentBeanManager clonePojo INFO: Third party instance, not cloned : org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed

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• Relationship between Repository and Unit of Work

  - by NullOrEmpty

  I am going to implement a repository, and I would like to use the UOW pattern since the consumer of the repository could do several operations, and I want to commit them at once. After read several articles about the matter, I still don't get how to relate this two elements, depending on the article it is being done in a way u other. Sometimes the UOW is something internal to the repository: public class Repository { UnitOfWork _uow; public Repository() { _uow = IoC.Get<UnitOfWork>(); } public void Save(Entity e) { _uow.Track(e); } public void SubmittChanges() { SaveInStorage(_uow.GetChanges()); } } And sometimes it is external: public class Repository { public void Save(Entity e, UnitOfWork uow) { uow.Track(e); } public void SubmittChanges(UnitOfWork uow) { SaveInStorage(uow.GetChanges()); } } Other times, is the UOW whom references the Repository public class UnitOfWork { Repository _repository; public UnitOfWork(Repository repository) { _repository = repository; } public void Save(Entity e) { this.Track(e); } public void SubmittChanges() { _repository.Save(this.GetChanges()); } } How are these two elements related? UOW tracks the elements that needs be changed, and repository contains the logic to persist those changes, but... who call who? Does the last make more sense? Also, who manages the connection? If several operations have to be done in the repository, I think using the same connection and even transaction is more sound, so maybe put the connection object inside the UOW and this one inside the repository makes sense as well. Cheers

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• How to print PCL Directly to the printer? Vb.net VS 2010

  - by Justin

  Good day, I've been trying to upgrade an old Print Program that prints raw pcl directly to the printer. The print program takes a PCL Mask and a PCL Batch Spool File (just pcl with page turn commands, I think) merges them and sends them off to the printer. I'm able to send to the Printer a file stream of PCL but I get mixed results and i do not understand why printing is so difficult under .net. I mean yes there is the PrintDocument class, but to print PCL... Let's just say I'm ready to detach my printer from the network and burn it a live. Here is my class PrintDirect (rather a hybrid class) Imports System Imports System.Text Imports System.Runtime.InteropServices <StructLayout(LayoutKind.Sequential)> _ Public Structure DOCINFO <MarshalAs(UnmanagedType.LPWStr)> _ Public pDocName As String <MarshalAs(UnmanagedType.LPWStr)> _ Public pOutputFile As String <MarshalAs(UnmanagedType.LPWStr)> _ Public pDataType As String End Structure 'DOCINFO Public Class PrintDirect <DllImport("winspool.drv", CharSet:=CharSet.Unicode, ExactSpelling:=False, CallingConvention:=CallingConvention.StdCall)> _ Public Shared Function OpenPrinter(ByVal pPrinterName As String, ByRef phPrinter As IntPtr, ByVal pDefault As Integer) As Long End Function <DllImport("winspool.drv", CharSet:=CharSet.Unicode, ExactSpelling:=False, CallingConvention:=CallingConvention.StdCall)> _ Public Shared Function StartDocPrinter(ByVal hPrinter As IntPtr, ByVal Level As Integer, ByRef pDocInfo As DOCINFO) As Long End Function <DllImport("winspool.drv", CharSet:=CharSet.Unicode, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _ Public Shared Function StartPagePrinter(ByVal hPrinter As IntPtr) As Long End Function <DllImport("winspool.drv", CharSet:=CharSet.Ansi, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _ Public Shared Function WritePrinter(ByVal hPrinter As IntPtr, ByVal data As String, ByVal buf As Integer, ByRef pcWritten As Integer) As Long End Function <DllImport("winspool.drv", CharSet:=CharSet.Unicode, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _ Public Shared Function EndPagePrinter(ByVal hPrinter As IntPtr) As Long End Function <DllImport("winspool.drv", CharSet:=CharSet.Unicode, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _ Public Shared Function EndDocPrinter(ByVal hPrinter As IntPtr) As Long End Function <DllImport("winspool.drv", CharSet:=CharSet.Unicode, ExactSpelling:=True, CallingConvention:=CallingConvention.StdCall)> _ Public Shared Function ClosePrinter(ByVal hPrinter As IntPtr) As Long End Function 'Helps uses to work with the printer Public Class PrintJob ''' <summary> ''' The address of the printer to print to. ''' </summary> ''' <remarks></remarks> Public PrinterName As String = "" Dim lhPrinter As New System.IntPtr() ''' <summary> ''' The object deriving from the Win32 API, Winspool.drv. ''' Use this object to overide the settings defined in the PrintJob Class. ''' </summary> ''' <remarks>Only use this when absolutly nessacary.</remarks> Public OverideDocInfo As New DOCINFO() ''' <summary> ''' The PCL Control Character or the ascii escape character. \x1b ''' </summary> ''' <remarks>ChrW(27)</remarks> Public Const PCL_Control_Character As Char = ChrW(27) ''' <summary> ''' Opens a connection to a printer, if false the connection could not be established. ''' </summary> ''' <returns></returns> ''' <remarks></remarks> Public Function OpenPrint() As Boolean Dim rtn_val As Boolean = False PrintDirect.OpenPrinter(PrinterName, lhPrinter, 0) If Not lhPrinter = 0 Then rtn_val = True End If Return rtn_val End Function ''' <summary> ''' The name of the Print Document. ''' </summary> ''' <value></value> ''' <returns></returns> ''' <remarks></remarks> Public Property DocumentName As String Get Return OverideDocInfo.pDocName End Get Set(ByVal value As String) OverideDocInfo.pDocName = value End Set End Property ''' <summary> ''' The type of Data that will be sent to the printer. ''' </summary> ''' <value>Send the print data type, usually "RAW" or "LPR". To overide use the OverideDocInfo Object</value> ''' <returns>The DataType as it was provided, if it is not part of the enumeration it is set to "UNKNOWN".</returns> ''' <remarks></remarks> Public Property DocumentDataType As PrintDataType Get Select Case OverideDocInfo.pDataType.ToUpper Case "RAW" Return PrintDataType.RAW Case "LPR" Return PrintDataType.LPR Case Else Return PrintDataType.UNKOWN End Select End Get Set(ByVal value As PrintDataType) OverideDocInfo.pDataType = [Enum].GetName(GetType(PrintDataType), value) End Set End Property Public Property DocumentOutputFile As String Get Return OverideDocInfo.pOutputFile End Get Set(ByVal value As String) OverideDocInfo.pOutputFile = value End Set End Property Enum PrintDataType UNKOWN = 0 RAW = 1 LPR = 2 End Enum ''' <summary> ''' Initializes the printing matrix ''' </summary> ''' <param name="PrintLevel">I have no idea what the hack this is...</param> ''' <remarks></remarks> Public Sub OpenDocument(Optional ByVal PrintLevel As Integer = 1) PrintDirect.StartDocPrinter(lhPrinter, PrintLevel, OverideDocInfo) End Sub ''' <summary> ''' Starts the next page. ''' </summary> ''' <remarks></remarks> Public Sub StartPage() PrintDirect.StartPagePrinter(lhPrinter) End Sub ''' <summary> ''' Writes a string to the printer, can be used to write out a section of the document at a time. ''' </summary> ''' <param name="data">The String to Send out to the Printer.</param> ''' <returns>The pcWritten as an integer, 0 may mean the writter did not write out anything.</returns> ''' <remarks>Warning the buffer is automatically created by the lenegth of the string.</remarks> Public Function WriteToPrinter(ByVal data As String) As Integer Dim pcWritten As Integer = 0 PrintDirect.WritePrinter(lhPrinter, data, data.Length - 1, pcWritten) Return pcWritten End Function Public Sub EndPage() PrintDirect.EndPagePrinter(lhPrinter) End Sub Public Sub CloseDocument() PrintDirect.EndDocPrinter(lhPrinter) End Sub Public Sub ClosePrint() PrintDirect.ClosePrinter(lhPrinter) End Sub ''' <summary> ''' Opens a connection to a printer and starts a new document. ''' </summary> ''' <returns>If false the connection could not be established. </returns> ''' <remarks></remarks> Public Function Open() As Boolean Dim rtn_val As Boolean = False rtn_val = OpenPrint() If rtn_val Then OpenDocument() End If Return rtn_val End Function ''' <summary> ''' Closes the document and closes the connection to the printer. ''' </summary> ''' <remarks></remarks> Public Sub Close() CloseDocument() ClosePrint() End Sub End Class End Class 'PrintDirect Here is how I print my file. I'm simple printing the PCL Masks, to show proof of concept. But I can't even do that. I can effectively create PCL and send it the printer without reading the file and it works fine... Plus I get mixed results with different stream reader text encoding as well. Dim pJob As New PrintDirect.PrintJob pJob.DocumentName = " test doc" pJob.DocumentDataType = PrintDirect.PrintJob.PrintDataType.RAW pJob.PrinterName = sPrinter.GetDevicePath '//This is where you'd stick your device name, sPrinter stands for Selected Printer from a dropdown (combobox). 'pJob.DocumentOutputFile = "C:\temp\test-spool.txt" If Not pJob.OpenPrint() Then MsgBox("Unable to connect to " & pJob.PrinterName, MsgBoxStyle.OkOnly, "Print Error") Exit Sub End If pJob.OpenDocument() pJob.StartPage() Dim sr As New IO.StreamReader(Me.txtFile.Text, Text.Encoding.ASCII) '//I've got best results with ASCII before, but only mized. Dim line As String = sr.ReadLine 'Fix for fly code on first run 'If line = 27 Then line = PrintDirect.PrintJob.PCL_Control_Character Do While (Not line Is Nothing) pJob.WriteToPrinter(line) line = sr.ReadLine Loop 'pJob.WriteToPrinter(ControlChars.FormFeed) pJob.EndPage() pJob.CloseDocument() sr.Close() sr.Dispose() sr = Nothing pJob.Close() I was able to get to print the mask, in the morning... now I'm getting strange printer characters scattered through 5 pages... I'm totally clueless. I must have changed something or the printer is at fault. You can access my test Check Mask, here http://kscserver.com/so/chk_mask.zip .

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• .LazyInitializationException when adding to a list that is held within a entity class using hibernat

  - by molleman

  Right so i am working with hibernate gilead and gwt to persist my data on users and files of a website. my users have a list of file locations. i am using annotations to map my classes to the database. i am getting a org.hibernate.LazyInitializationException when i try to add file locations to the list that is held in the user class. this is a method below that is overridden from a external file upload servlet class that i am using. when the file uploads it calls this method. the user1 is loaded from the database elsewhere. the exception occurs at user1.getFileLocations().add(fileLocation); . i dont understand it really at all.! any help would be great. the stack trace of the error is below public String executeAction(HttpServletRequest request, List<FileItem> sessionFiles) throws UploadActionException { for (FileItem item : sessionFiles) { if (false == item.isFormField()) { try { YFUser user1 = (YFUser)getSession().getAttribute(SESSION_USER); // This is the location where a file will be stored String fileLocationString = "/Users/Stefano/Desktop/UploadedFiles/" + user1.getUsername(); File fl = new File(fileLocationString); fl.mkdir(); // so here i will create the a file container for my uploaded file File file = File.createTempFile("upload-", ".bin",fl); // this is where the file is written to disk item.write(file); // the FileLocation object is then created FileLocation fileLocation = new FileLocation(); fileLocation.setLocation(fileLocationString); //test System.out.println("file path = "+file.getPath()); user1.getFileLocations().add(fileLocation); //the line above is where the exception occurs } catch (Exception e) { throw new UploadActionException(e.getMessage()); } } removeSessionFileItems(request); } return null; } //This is the class file for a Your Files User @Entity @Table(name = "yf_user_table") public class YFUser implements Serializable,ILightEntity { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "user_id",nullable = false) private int userId; @Column(name = "username") private String username; @Column(name = "password") private String password; @Column(name = "email") private String email; @ManyToMany(cascade = CascadeType.ALL) @JoinTable(name = "USER_FILELOCATION", joinColumns = { @JoinColumn(name = "user_id") }, inverseJoinColumns = { @JoinColumn(name = "locationId") }) private List<FileLocation> fileLocations = new ArrayList<FileLocation>() ; public YFUser(){ } public int getUserId() { return userId; } private void setUserId(int userId) { this.userId = userId; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public List<FileLocation> getFileLocations() { if(fileLocations ==null){ fileLocations = new ArrayList<FileLocation>(); } return fileLocations; } public void setFileLocations(List<FileLocation> fileLocations) { this.fileLocations = fileLocations; } /* public void addFileLocation(FileLocation location){ fileLocations.add(location); }*/ @Override public void addProxyInformation(String property, Object proxyInfo) { // TODO Auto-generated method stub } @Override public String getDebugString() { // TODO Auto-generated method stub return null; } @Override public Object getProxyInformation(String property) { // TODO Auto-generated method stub return null; } @Override public boolean isInitialized(String property) { // TODO Auto-generated method stub return false; } @Override public void removeProxyInformation(String property) { // TODO Auto-generated method stub } @Override public void setInitialized(String property, boolean initialised) { // TODO Auto-generated method stub } @Override public Object getValue() { // TODO Auto-generated method stub return null; } } @Entity @Table(name = "fileLocationTable") public class FileLocation implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "locationId", updatable = false, nullable = false) private int ieId; @Column (name = "location") private String location; /* private List uploadedUsers = new ArrayList(); */ public FileLocation(){ } public int getIeId() { return ieId; } private void setIeId(int ieId) { this.ieId = ieId; } public String getLocation() { return location; } public void setLocation(String location) { this.location = location; } /* public List getUploadedUsers() { return uploadedUsers; } public void setUploadedUsers(List<YFUser> uploadedUsers) { this.uploadedUsers = uploadedUsers; } public void addUploadedUser(YFUser user){ uploadedUsers.add(user); } */ } Apr 2, 2010 11:33:12 PM org.hibernate.LazyInitializationException <init> SEVERE: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:380) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:372) at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:365) at org.hibernate.collection.AbstractPersistentCollection.write(AbstractPersistentCollection.java:205) at org.hibernate.collection.PersistentBag.add(PersistentBag.java:297) at com.example.server.TestServiceImpl.saveFileLocation(TestServiceImpl.java:132) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at net.sf.gilead.gwt.PersistentRemoteService.processCall(PersistentRemoteService.java:174) at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:224) at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62) at javax.servlet.http.HttpServlet.service(HttpServlet.java:713) at javax.servlet.http.HttpServlet.service(HttpServlet.java:806) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:324) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:396) at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488) Apr 2, 2010 11:33:12 PM net.sf.gilead.core.PersistentBeanManager clonePojo INFO: Third party instance, not cloned : org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.client.YFUser.fileLocations, no session or session was closed

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• C# delegates problem

  - by Mick Taylor

  Hello I am getting the following error from my C# Windows Application: Error 1 No overload for 'CreateLabelInPanel' matches delegate 'WorksOrderStore.ProcessDbConnDetailsDelegate' H:\c\WorksOrderFactory\WorksOrderFactory\WorksOrderClient.cs 43 39 WorksOrderFactory I have 3 .cs files that essentially: Opens a windows Has an option for the users to connect to a db When that is selected, the system will go off and connect to the db, and load some data in (just test data for now) Then using a delegate, the system should do soemthing, which for testing will be to create a label. However I haven't coded this part yet. But I can't build until I get this error sorted. The 3 fiels are called: WorksOrderClient.cs (which is the MAIN) WorksOrderStore.cs LoginBox.cs Here's the code for each file: WorksOrderClient.cs using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using WorksOrderStore; namespace WorksOrderFactory { using WorksOrderStore; public partial class WorksOrderClient : Form { LoginBox lb = new LoginBox(); private static WorksOrderDB wodb = new WorksOrderDB(); private static int num_conns = 0; public WorksOrderClient() { InitializeComponent(); } private void connectToADBToolStripMenuItem_Click(object sender, EventArgs e) { lb.ShowDialog(); lb.Visible = true; } public static bool createDBConnDetObj(string username, string password, string database) { // increase the number of connections num_conns = num_conns + 1; // create the connection object wodb.AddDbConnDetails(username, password, database, num_conns); // create a new delegate object associated with the static // method WorksOrderClient.createLabelInPanel wodb.ProcessDbConnDetails(new ProcessDbConnDetailsDelegate(CreateLabelInPanel)); return true; } static void CreateLabelInPanel(DbConnDetails dbcd) { Console.Write("hellO"); string tmp = (string)dbcd.username; //Console.Write(tmp); } private void WorksOrderClient_Load(object sender, EventArgs e) { } } } WorksOrderStore.cs using System; using System.Collections.Generic; using System.Linq; using System.Text; using WorksOrderFactory; namespace WorksOrderStore { using System.Collections; // Describes a book in the book list: public struct WorksOrder { public string contractor_code { get; set; } // contractor ID public string email_address { get; set; } // contractors email address public string date_issued { get; set; } // date the works order was issued public string wo_ref { get; set; } // works order ref public string status { get; set; } // status ... not used public job_status js { get; set; } // status of this worksorder within this system public WorksOrder(string contractor_code, string email_address, string date_issued, string wo_ref) : this() { this.contractor_code = contractor_code; this.email_address = email_address; this.date_issued = date_issued; this.wo_ref = wo_ref; this.js = job_status.Pending; } } // Declare a delegate type for processing a WorksOrder: //public delegate void ProcessWorksOrderDelegate(WorksOrder worksorder); // Maintains a worksorder database. public class WorksOrderDB { // List of all worksorders in the database: ArrayList list = new ArrayList(); // Add a worksorder to the database: public void AddWorksOrder(string contractor_code, string email_address, string date_issued, string wo_ref) { list.Add(new WorksOrder(contractor_code, email_address, date_issued, wo_ref)); } // Call a passed-in delegate on each pending works order to process it: /*public void ProcessPendingWorksOrders(ProcessWorksOrderDelegate processWorksOrder) { foreach (WorksOrder wo in list) { if (wo.js.Equals(job_status.Pending)) // Calling the delegate: processWorksOrder(wo); } }*/ // Add a DbConnDetails to the database: public void AddDbConnDetails(string username, string password, string database, int conn_num) { list.Add(new DbConnDetails(username, password, database, conn_num)); } // Call a passed-in delegate on each dbconndet to process it: public void ProcessDbConnDetails(ProcessDbConnDetailsDelegate processDBConnDetails) { foreach (DbConnDetails wo in list) { processDBConnDetails(wo); } } } // statuses for worksorders in this system public enum job_status { Pending, InProgress, Completed } public struct DbConnDetails { public string username { get; set; } // username public string password { get; set; } // password public string database { get; set; } // database public int conn_num { get; set; } // this objects connection number. public ArrayList woList { get; set; } // list of works orders for this connection // this constructor just sets the db connection details // the woList array will get created later .. not a lot later but a bit. public DbConnDetails(string username, string password, string database, int conn_num) : this() { this.username = username; this.password = password; this.database = database; this.conn_num = conn_num; woList = new ArrayList(); } } // Declare a delegate type for processing a DbConnDetails: public delegate void ProcessDbConnDetailsDelegate(DbConnDetails dbConnDetails); } and LoginBox.cs using System; using System.Collections.Generic; using System.ComponentModel; using System.Drawing; using System.Data; using System.Linq; using System.Text; using System.Windows.Forms; namespace WorksOrderFactory { public partial class LoginBox : Form { public LoginBox() { InitializeComponent(); } private void LoginBox_Load(object sender, EventArgs e) { this.Visible = true; this.Show(); //usernameText.Text = "Username"; //new Font(usernameText.Font, FontStyle.Italic); } private void cancelBtn_Click(object sender, EventArgs e) { this.Close(); } private void loginBtn_Click(object sender, EventArgs e) { // set up a connection details object. bool success = WorksOrderClient.createDBConnDetObj(usernameText.Text, passwordText.Text, databaseText.Text); } private void LoginBox_Load_1(object sender, EventArgs e) { } } } Any ideas?? Cheers, m

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• Understanding C# async / await (1) Compilation

  - by Dixin

  Now the async / await keywords are in C#. Just like the async and ! in F#, this new C# feature provides great convenience. There are many nice documents talking about how to use async / await in specific scenarios, like using async methods in ASP.NET 4.5 and in ASP.NET MVC 4, etc. In this article we will look at the real code working behind the syntax sugar. According to MSDN: The async modifier indicates that the method, lambda expression, or anonymous method that it modifies is asynchronous. Since lambda expression / anonymous method will be compiled to normal method, we will focus on normal async method. Preparation First of all, Some helper methods need to make up. internal class HelperMethods { internal static int Method(int arg0, int arg1) { // Do some IO. WebClient client = new WebClient(); Enumerable.Repeat("http://weblogs.asp.net/dixin", 10) .Select(client.DownloadString).ToArray(); int result = arg0 + arg1; return result; } internal static Task<int> MethodTask(int arg0, int arg1) { Task<int> task = new Task<int>(() => Method(arg0, arg1)); task.Start(); // Hot task (started task) should always be returned. return task; } internal static void Before() { } internal static void Continuation1(int arg) { } internal static void Continuation2(int arg) { } } Here Method() is a long running method doing some IO. Then MethodTask() wraps it into a Task and return that Task. Nothing special here. Await something in async method Since MethodTask() returns Task, let’s try to await it: internal class AsyncMethods { internal static async Task<int> MethodAsync(int arg0, int arg1) { int result = await HelperMethods.MethodTask(arg0, arg1); return result; } } Because we used await in the method, async must be put on the method. Now we get the first async method. According to the naming convenience, it is named MethodAsync. Of course a async method can be awaited. So we have a CallMethodAsync() to call MethodAsync(): internal class AsyncMethods { internal static async Task<int> CallMethodAsync(int arg0, int arg1) { int result = await MethodAsync(arg0, arg1); return result; } } After compilation, MethodAsync() and CallMethodAsync() becomes the same logic. This is the code of MethodAsyc(): internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MethodAsync(int arg0, int arg1) { MethodAsyncStateMachine methodAsyncStateMachine = new MethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; methodAsyncStateMachine.Builder.Start(ref methodAsyncStateMachine); return methodAsyncStateMachine.Builder.Task; } } It just creates and starts a state machine, MethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Result; private TaskAwaiter<int> awaitor; void IAsyncStateMachine.MoveNext() { try { if (this.State != 0) { this.awaitor = HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaitor.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaitor, ref this); return; } } else { this.State = -1; } this.Result = this.awaitor.GetResult(); } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); return; } this.State = -2; this.Builder.SetResult(this.Result); } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine param0) { this.Builder.SetStateMachine(param0); } } The generated code has been refactored, so it is readable and can be compiled. Several things can be observed here: The async modifier is gone, which shows, unlike other modifiers (e.g. static), there is no such IL/CLR level “async” stuff. It becomes a AsyncStateMachineAttribute. This is similar to the compilation of extension method. The generated state machine is very similar to the state machine of C# yield syntax sugar. The local variables (arg0, arg1, result) are compiled to fields of the state machine. The real code (await HelperMethods.MethodTask(arg0, arg1)) is compiled into MoveNext(): HelperMethods.MethodTask(this.Arg0, this.Arg1).GetAwaiter(). CallMethodAsync() will create and start its own state machine CallMethodAsyncStateMachine: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(CallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> CallMethodAsync(int arg0, int arg1) { CallMethodAsyncStateMachine callMethodAsyncStateMachine = new CallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; callMethodAsyncStateMachine.Builder.Start(ref callMethodAsyncStateMachine); return callMethodAsyncStateMachine.Builder.Task; } } CallMethodAsyncStateMachine has the same logic as MethodAsyncStateMachine above. The detail of the state machine will be discussed soon. Now it is clear that: async /await is a C# language level syntax sugar. There is no difference to await a async method or a normal method. As long as a method returns Task, it is awaitable. State machine and continuation To demonstrate more details in the state machine, a more complex method is created: internal class AsyncMethods { internal static async Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; } } In this method: There are multiple awaits. There are code before the awaits, and continuation code after each await After compilation, this multi-await method becomes the same as above single-await methods: internal class CompiledAsyncMethods { [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, Builder = AsyncTaskMethodBuilder<int>.Create(), State = -1 }; multiCallMethodAsyncStateMachine.Builder.Start(ref multiCallMethodAsyncStateMachine); return multiCallMethodAsyncStateMachine.Builder.Task; } } It creates and starts one single state machine, MultiCallMethodAsyncStateMachine: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { public int State; public AsyncTaskMethodBuilder<int> Builder; public int Arg0; public int Arg1; public int Arg2; public int Arg3; public int ResultOfAwait1; public int ResultOfAwait2; public int ResultToReturn; private TaskAwaiter<int> awaiter; void IAsyncStateMachine.MoveNext() { try { switch (this.State) { case -1: HelperMethods.Before(); this.awaiter = AsyncMethods.MethodAsync(this.Arg0, this.Arg1).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 0; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 0: this.ResultOfAwait1 = this.awaiter.GetResult(); HelperMethods.Continuation1(this.ResultOfAwait1); this.awaiter = AsyncMethods.MethodAsync(this.Arg2, this.Arg3).GetAwaiter(); if (!this.awaiter.IsCompleted) { this.State = 1; this.Builder.AwaitUnsafeOnCompleted(ref this.awaiter, ref this); } break; case 1: this.ResultOfAwait2 = this.awaiter.GetResult(); HelperMethods.Continuation2(this.ResultOfAwait2); this.ResultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; this.State = -2; this.Builder.SetResult(this.ResultToReturn); break; } } catch (Exception exception) { this.State = -2; this.Builder.SetException(exception); } } [DebuggerHidden] void IAsyncStateMachine.SetStateMachine(IAsyncStateMachine stateMachine) { this.Builder.SetStateMachine(stateMachine); } } Once again, the above state machine code is already refactored, but it still has a lot of things. More clean up can be done if we only keep the core logic, and the state machine can become very simple: [CompilerGenerated] [StructLayout(LayoutKind.Auto)] internal struct MultiCallMethodAsyncStateMachine : IAsyncStateMachine { // State: // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End public int State; public TaskCompletionSource<int> ResultToReturn; // int resultToReturn ... public int Arg0; // int Arg0 public int Arg1; // int arg1 public int Arg2; // int arg2 public int Arg3; // int arg3 public int ResultOfAwait1; // int resultOfAwait1 ... public int ResultOfAwait2; // int resultOfAwait2 ... private Task<int> currentTaskToAwait; /// <summary> /// Moves the state machine to its next state. /// </summary> public void MoveNext() // IAsyncStateMachine member. { try { switch (this.State) { // Original code is split by "await"s into "case"s: // case -1: // HelperMethods.Before(); // MethodAsync(Arg0, arg1); // case 0: // int resultOfAwait1 = await ... // HelperMethods.Continuation1(resultOfAwait1); // MethodAsync(arg2, arg3); // case 1: // int resultOfAwait2 = await ... // HelperMethods.Continuation2(resultOfAwait2); // int resultToReturn = resultOfAwait1 + resultOfAwait2; // return resultToReturn; case -1: // -1 is begin. HelperMethods.Before(); // Code before 1st await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg0, this.Arg1); // 1st task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 0. this.State = 0; MultiCallMethodAsyncStateMachine that1 = this; // Cannot use "this" in lambda so create a local variable. this.currentTaskToAwait.ContinueWith(_ => that1.MoveNext()); break; case 0: // Now 1st await is done. this.ResultOfAwait1 = this.currentTaskToAwait.Result; // Get 1st await's result. HelperMethods.Continuation1(this.ResultOfAwait1); // Code after 1st await and before 2nd await. this.currentTaskToAwait = AsyncMethods.MethodAsync(this.Arg2, this.Arg3); // 2nd task to await // When this.currentTaskToAwait is done, run this.MoveNext() and go to case 1. this.State = 1; MultiCallMethodAsyncStateMachine that2 = this; this.currentTaskToAwait.ContinueWith(_ => that2.MoveNext()); break; case 1: // Now 2nd await is done. this.ResultOfAwait2 = this.currentTaskToAwait.Result; // Get 2nd await's result. HelperMethods.Continuation2(this.ResultOfAwait2); // Code after 2nd await. int resultToReturn = this.ResultOfAwait1 + this.ResultOfAwait2; // Code after 2nd await. // End with resultToReturn. this.State = -2; // -2 is end. this.ResultToReturn.SetResult(resultToReturn); break; } } catch (Exception exception) { // End with exception. this.State = -2; // -2 is end. this.ResultToReturn.SetException(exception); } } /// <summary> /// Configures the state machine with a heap-allocated replica. /// </summary> /// <param name="stateMachine">The heap-allocated replica.</param> [DebuggerHidden] public void SetStateMachine(IAsyncStateMachine stateMachine) // IAsyncStateMachine member. { // No core logic. } } Only Task and TaskCompletionSource are involved in this version. And MultiCallMethodAsync() can be simplified to: [DebuggerStepThrough] [AsyncStateMachine(typeof(MultiCallMethodAsyncStateMachine))] // async internal static /*async*/ Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { MultiCallMethodAsyncStateMachine multiCallMethodAsyncStateMachine = new MultiCallMethodAsyncStateMachine() { Arg0 = arg0, Arg1 = arg1, Arg2 = arg2, Arg3 = arg3, ResultToReturn = new TaskCompletionSource<int>(), // -1: Begin // 0: 1st await is done // 1: 2nd await is done // ... // -2: End State = -1 }; multiCallMethodAsyncStateMachine.MoveNext(); // Original code are moved into this method. return multiCallMethodAsyncStateMachine.ResultToReturn.Task; } Now the whole state machine becomes very clean - it is about callback: Original code are split into pieces by “await”s, and each piece is put into each “case” in the state machine. Here the 2 awaits split the code into 3 pieces, so there are 3 “case”s. The “piece”s are chained by callback, that is done by Builder.AwaitUnsafeOnCompleted(callback), or currentTaskToAwait.ContinueWith(callback) in the simplified code. A previous “piece” will end with a Task (which is to be awaited), when the task is done, it will callback the next “piece”. The state machine’s state works with the “case”s to ensure the code “piece”s executes one after another. Callback If we focus on the point of callback, the simplification  can go even further – the entire state machine can be completely purged, and we can just keep the code inside MoveNext(). Now MultiCallMethodAsync() becomes: internal static Task<int> MultiCallMethodAsync(int arg0, int arg1, int arg2, int arg3) { TaskCompletionSource<int> taskCompletionSource = new TaskCompletionSource<int>(); try { // Oringinal code begins. HelperMethods.Before(); MethodAsync(arg0, arg1).ContinueWith(await1 => { int resultOfAwait1 = await1.Result; HelperMethods.Continuation1(resultOfAwait1); MethodAsync(arg2, arg3).ContinueWith(await2 => { int resultOfAwait2 = await2.Result; HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; // Oringinal code ends. taskCompletionSource.SetResult(resultToReturn); }); }); } catch (Exception exception) { taskCompletionSource.SetException(exception); } return taskCompletionSource.Task; } Please compare with the original async / await code: HelperMethods.Before(); int resultOfAwait1 = await MethodAsync(arg0, arg1); HelperMethods.Continuation1(resultOfAwait1); int resultOfAwait2 = await MethodAsync(arg2, arg3); HelperMethods.Continuation2(resultOfAwait2); int resultToReturn = resultOfAwait1 + resultOfAwait2; return resultToReturn; Yeah that is the magic of C# async / await: Await is not to wait. In a await expression, a Task object will be return immediately so that execution is not blocked. The continuation code is compiled as that Task’s callback code. When that task is done, continuation code will execute. Please notice that many details inside the state machine are omitted for simplicity, like context caring, etc. If you want to have a detailed picture, please do check out the source code of AsyncTaskMethodBuilder and TaskAwaiter.

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• Replacing “if”s with your own number system

  - by Michael Williamson

  During our second code retreat at Red Gate, the restriction for one of the sessions was disallowing the use of if statements. That includes other constructs that have the same effect, such as switch statements or loops that will only be executed zero or one times. The idea is to encourage use of polymorphism instead, and see just how far it can be used to get rid of “if”s. The main place where people struggled to get rid of numbers from their implementation of Conway’s Game of Life was the piece of code that decides whether a cell is live or dead in the next generation. For instance, for a cell that’s currently live, the code might look something like this: if (numberOfNeighbours == 2 || numberOfNeighbours == 3) { return CellState.LIVE; } else { return CellState.DEAD; } The problem is that we need to change behaviour depending on the number of neighbours each cell has, but polymorphism only allows us to switch behaviour based on the type of a value. It follows that the solution is to make different numbers have different types: public interface IConwayNumber { IConwayNumber Increment(); CellState LiveCellNextGeneration(); } public class Zero : IConwayNumber { public IConwayNumber Increment() { return new One(); } public CellState LiveCellNextGeneration() { return CellState.DEAD; } } public class One : IConwayNumber { public IConwayNumber Increment() { return new Two(); } public CellState LiveCellNextGeneration() { return CellState.LIVE; } } public class Two : IConwayNumber { public IConwayNumber Increment() { return new ThreeOrMore(); } public CellState LiveCellNextGeneration() { return CellState.LIVE; } } public class ThreeOrMore : IConwayNumber { public IConwayNumber Increment() { return this; } public CellState LiveCellNextGeneration() { return CellState.DEAD; } } In the code that counts the number of neighbours, we use our new number system by starting with Zero and incrementing when we find a neighbour. To choose the next state of the cell, rather than inspecting the number of neighbours, we ask the number of neighbours for the next state directly: return numberOfNeighbours.LiveCellNextGeneration(); And now we have no “if”s! If C# had double-dispatch, or if we used the visitor pattern, we could move the logic for choosing the next cell out of the number classes, which might feel a bit more natural. I suspect that reimplementing the natural numbers is still going to feel about the same amount of crazy though.

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• How to handle "circular dependency" in dependency injection

  - by Roel

  The title says "Circular Dependency", but it is not the correct wording, because to me the design seems solid. However, consider the following scenario, where the blue parts are given from external partner, and orange is my own implementation. Also assume there is more then one ConcreteMain, but I want to use a specific one. (In reality, each class has some more dependencies, but I tried to simplify it here) I would like to instanciate all of this with Depency Injection (Unity), but I obviously get a StackOverflowException on the following code, because Runner tries to instantiate ConcreteMain, and ConcreteMain needs a Runner. IUnityContainer ioc = new UnityContainer(); ioc.RegisterType<IMain, ConcreteMain>() .RegisterType<IMainCallback, Runner>(); var runner = ioc.Resolve<Runner>(); How can I avouid this? Is there any way to structure this so that I can use it with DI? The scenario I'm doing now is setting everything up manually, but that puts a hard dependency on ConcreteMain in the class which instantiates it. This is what i'm trying to avoid (with Unity registrations in configuration). All source code below (very simplified example!); public class Program { public static void Main(string[] args) { IUnityContainer ioc = new UnityContainer(); ioc.RegisterType<IMain, ConcreteMain>() .RegisterType<IMainCallback, Runner>(); var runner = ioc.Resolve<Runner>(); Console.WriteLine("invoking runner..."); runner.DoSomethingAwesome(); Console.ReadLine(); } } public class Runner : IMainCallback { private readonly IMain mainServer; public Runner(IMain mainServer) { this.mainServer = mainServer; } public void DoSomethingAwesome() { Console.WriteLine("trying to do something awesome"); mainServer.DoSomething(); } public void SomethingIsDone(object something) { Console.WriteLine("hey look, something is finally done."); } } public interface IMain { void DoSomething(); } public interface IMainCallback { void SomethingIsDone(object something); } public abstract class AbstractMain : IMain { protected readonly IMainCallback callback; protected AbstractMain(IMainCallback callback) { this.callback = callback; } public abstract void DoSomething(); } public class ConcreteMain : AbstractMain { public ConcreteMain(IMainCallback callback) : base(callback){} public override void DoSomething() { Console.WriteLine("starting to do something..."); var task = Task.Factory.StartNew(() =>{ Thread.Sleep(5000);/*very long running task*/ }); task.ContinueWith(t => callback.SomethingIsDone(true)); } }

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• Loading class instance from XML with Texture2D

  - by Thegluestickman

  I'm having trouble with XML and XNA. I want to be able to load weapon settings through XML to make my weapons easier to make and to have less code in the actual project file. So I started out making a basic XML document, something to just assign variables with. But no matter what I changed it gave me a new error every time. The code below gives me a "XML element 'Tag' not found", I added and it started to say the variables weren't found. What I wanted to do in the XML file as well, was load a texture for the file too. So I created a static class to hold my texture values, then in the Texture tag of my XML document I would set it to that instance too. I think that's were the problems are occuring because that's where the "XML element 'Tag' not found" error is pointing me too. My XML document: <XnaContent> <Asset Type="ConversationEngine.Weapon"> <weaponStrength>0</weaponStrength> <damageModifiers>0</damageModifiers> <speed>0</speed> <magicDefense>0</magicDefense> <description>0</description> <identifier>0</identifier> <weaponTexture>LoadWeaponTextures.ironSword</weaponTexture> </Asset> </XnaContent> My Class to load the weapon XML: public class Weapon { public int weaponStrength; public int damageModifiers; public int speed; public int magicDefense; public string description; public string identifier; public Texture2D weaponTexture; } public static class LoadWeaponXML { static Weapon Weapons; public static Weapon WeaponLoad(ContentManager content, int id) { Weapons = content.Load<Weapon>(@"Weapons/" + id); return Weapons; } } public static class LoadWeaponTextures { public static Texture2D ironSword; public static void TextureLoad(ContentManager content) { ironSword = content.Load<Texture2D>("Sword"); } } I'm not entirely sure if you can load textures through XML, but any help would be greatly appreciated.

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• Using the jQuery UI Library in a MVC 3 Application to Build a Dialog Form

  - by ChrisD

  Using a simulated dialog window is a nice way to handle inline data editing. The jQuery UI has a UI widget for a dialog window that makes it easy to get up and running with it in your application. With the release of ASP.NET MVC 3, Microsoft included the jQuery UI scripts and files in the MVC 3 project templates for Visual Studio. With the release of the MVC 3 Tools Update, Microsoft implemented the inclusion of those with NuGet as packages. That means we can get up and running using the latest version of the jQuery UI with minimal effort. To the code! Another that might interested you about JQuery Mobile and ASP.NET MVC 3 with C#. If you are starting with a new MVC 3 application and have the Tools Update then you are a NuGet update and a <link> and <script> tag away from adding the jQuery UI to your project. If you are using an existing MVC project you can still get the jQuery UI library added to your project via NuGet and then add the link and script tags. Assuming that you have pulled down the latest version (at the time of this publish it was 1.8.13) you can add the following link and script tags to your <head> tag: < link href = "@Url.Content(" ~ / Content / themes / base / jquery . ui . all . css ")" rel = "Stylesheet" type = "text/css" /> < script src = "@Url.Content(" ~ / Scripts / jquery-ui-1 . 8 . 13 . min . js ")" type = "text/javascript" ></ script > The jQuery UI library relies upon the CSS scripts and some image files to handle rendering of its widgets (you can choose a different theme or role your own if you like). Adding these to the stock _Layout.cshtml file results in the following markup: <!DOCTYPE html> < html > < head >     < meta charset = "utf-8" />     < title > @ViewBag.Title </ title >     < link href = "@Url.Content(" ~ / Content / Site . css ")" rel = "stylesheet" type = "text/css" />     <link href="@Url.Content("~/Content/themes/base/jquery.ui.all.css")" rel="Stylesheet" type="text/css" />     <script src="@Url.Content("~/Scripts/jquery-1.5.1.min.js")" type="text/javascript"></script>     <script src="@Url.Content("~/Scripts/modernizr-1.7.min . js ")" type = "text/javascript" ></ script >     < script src = "@Url.Content(" ~ / Scripts / jquery-ui-1 . 8 . 13 . min . js ")" type = "text/javascript" ></ script > </ head > < body >     @RenderBody() </ body > </ html > Our example will involve building a list of notes with an id, title and description. Each note can be edited and new notes can be added. The user will never have to leave the single page of notes to manage the note data. The add and edit forms will be delivered in a jQuery UI dialog widget and the note list content will get reloaded via an AJAX call after each change to the list. To begin, we need to craft a model and a data management class. We will do this so we can simulate data storage and get a feel for the workflow of the user experience. The first class named Note will have properties to represent our data model. namespace Website . Models {     public class Note     {         public int Id { get ; set ; }         public string Title { get ; set ; }         public string Body { get ; set ; }     } } The second class named NoteManager will be used to set up our simulated data storage and provide methods for querying and updating the data. We will take a look at the class content as a whole and then walk through each method after. using System . Collections . ObjectModel ; using System . Linq ; using System . Web ; namespace Website . Models {     public class NoteManager     {         public Collection < Note > Notes         {             get             {                 if ( HttpRuntime . Cache [ "Notes" ] == null )                     this . loadInitialData ();                 return ( Collection < Note >) HttpRuntime . Cache [ "Notes" ];             }         }         private void loadInitialData ()         {             var notes = new Collection < Note >();             notes . Add ( new Note                           {                               Id = 1 ,                               Title = "Set DVR for Sunday" ,                               Body = "Don't forget to record Game of Thrones!"                           });             notes . Add ( new Note                           {                               Id = 2 ,                               Title = "Read MVC article" ,                               Body = "Check out the new iwantmymvc.com post"                           });             notes . Add ( new Note                           {                               Id = 3 ,                               Title = "Pick up kid" ,                               Body = "Daughter out of school at 1:30pm on Thursday. Don't forget!"                           });             notes . Add ( new Note                           {                               Id = 4 ,                               Title = "Paint" ,                               Body = "Finish the 2nd coat in the bathroom"                           });             HttpRuntime . Cache [ "Notes" ] = notes ;         }         public Collection < Note > GetAll ()         {             return Notes ;         }         public Note GetById ( int id )         {             return Notes . Where ( i => i . Id == id ). FirstOrDefault ();         }         public int Save ( Note item )         {             if ( item . Id <= 0 )                 return saveAsNew ( item );             var existingNote = Notes . Where ( i => i . Id == item . Id ). FirstOrDefault ();             existingNote . Title = item . Title ;             existingNote . Body = item . Body ;             return existingNote . Id ;         }         private int saveAsNew ( Note item )         {             item . Id = Notes . Count + 1 ;             Notes . Add ( item );             return item . Id ;         }     } } The class has a property named Notes that is read only and handles instantiating a collection of Note objects in the runtime cache if it doesn't exist, and then returns the collection from the cache. This property is there to give us a simulated storage so that we didn't have to add a full blown database (beyond the scope of this post). The private method loadInitialData handles pre-filling the collection of Note objects with some initial data and stuffs them into the cache. Both of these chunks of code would be refactored out with a move to a real means of data storage. The GetAll and GetById methods access our simulated data storage to return all of our notes or a specific note by id. The Save method takes in a Note object, checks to see if it has an Id less than or equal to zero (we assume that an Id that is not greater than zero represents a note that is new) and if so, calls the private method saveAsNew . If the Note item sent in has an Id , the code finds that Note in the simulated storage, updates the Title and Description , and returns the Id value. The saveAsNew method sets the Id , adds it to the simulated storage, and returns the Id value. The increment of the Id is simulated here by getting the current count of the note collection and adding 1 to it. The setting of the Id is the only other chunk of code that would be refactored out when moving to a different data storage approach. With our model and data manager code in place we can turn our attention to the controller and views. We can do all of our work in a single controller. If we use a HomeController , we can add an action method named Index that will return our main view. An action method named List will get all of our Note objects from our manager and return a partial view. We will use some jQuery to make an AJAX call to that action method and update our main view with the partial view content returned. Since the jQuery AJAX call will cache the call to the content in Internet Explorer by default (a setting in jQuery), we will decorate the List, Create and Edit action methods with the OutputCache attribute and a duration of 0. This will send the no-cache flag back in the header of the content to the browser and jQuery will pick that up and not cache the AJAX call. The Create action method instantiates a new Note model object and returns a partial view, specifying the NoteForm.cshtml view file and passing in the model. The NoteForm view is used for the add and edit functionality. The Edit action method takes in the Id of the note to be edited, loads the Note model object based on that Id , and does the same return of the partial view as the Create method. The Save method takes in the posted Note object and sends it to the manager to save. It is decorated with the HttpPost attribute to ensure that it will only be available via a POST. It returns a Json object with a property named Success that can be used by the UX to verify everything went well (we won't use that in our example). Both the add and edit actions in the UX will post to the Save action method, allowing us to reduce the amount of unique jQuery we need to write in our view. The contents of the HomeController.cs file: using System . Web . Mvc ; using Website . Models ; namespace Website . Controllers {     public class HomeController : Controller     {         public ActionResult Index ()         {             return View ();         }         [ OutputCache ( Duration = 0 )]         public ActionResult List ()         {             var manager = new NoteManager ();             var model = manager . GetAll ();             return PartialView ( model );         }         [ OutputCache ( Duration = 0 )]         public ActionResult Create ()         {             var model = new Note ();             return PartialView ( "NoteForm" , model );         }         [ OutputCache ( Duration = 0 )]         public ActionResult Edit ( int id )         {             var manager = new NoteManager ();             var model = manager . GetById ( id );             return PartialView ( "NoteForm" , model );         }         [ HttpPost ]         public JsonResult Save ( Note note )         {             var manager = new NoteManager ();             var noteId = manager . Save ( note );             return Json ( new { Success = noteId > 0 });         }     } } The view for the note form, NoteForm.cshtml , looks like so: @model Website . Models . Note @using ( Html . BeginForm ( "Save" , "Home" , FormMethod . Post , new { id = "NoteForm" })) { @Html . Hidden ( "Id" ) < label class = "Title" >     < span > Title < /span><br / >     @Html . TextBox ( "Title" ) < /label> <label class="Body">     <span>Body</ span >< br />     @Html . TextArea ( "Body" ) < /label> } It is a strongly typed view for our Note model class. We give the <form> element an id attribute so that we can reference it via jQuery. The <label> and <span> tags give our UX some structure that we can style with some CSS. The List.cshtml view is used to render out a <ul> element with all of our notes. @model IEnumerable < Website . Models . Note > < ul class = "NotesList" >     @foreach ( var note in Model )     {     < li >         @note . Title < br />         @note . Body < br />         < span class = "EditLink ButtonLink" noteid = "@note.Id" > Edit < /span>     </ li >     } < /ul> This view is strongly typed as well. It includes a <span> tag that we will use as an edit button. We add a custom attribute named noteid to the <span> tag that we can use in our jQuery to identify the Id of the note object we want to edit. The view, Index.cshtml , contains a bit of html block structure and all of our jQuery logic code. @ {     ViewBag . Title = "Index" ; } < h2 > Notes < /h2> <div id="NoteListBlock"></ div > < span class = "AddLink ButtonLink" > Add New Note < /span> <div id="NoteDialog" title="" class="Hidden"></ div > < script type = "text/javascript" >     $ ( function () {         $ ( "#NoteDialog" ). dialog ({             autoOpen : false , width : 400 , height : 330 , modal : true ,             buttons : {                 "Save" : function () {                     $ . post ( "/Home/Save" ,                         $ ( "#NoteForm" ). serialize (),                         function () {                             $ ( "#NoteDialog" ). dialog ( "close" );                             LoadList ();                         });                 },                 Cancel : function () { $ ( this ). dialog ( "close" ); }             }         });         $ ( ".EditLink" ). live ( "click" , function () {             var id = $ ( this ). attr ( "noteid" );             $ ( "#NoteDialog" ). html ( "" )                 . dialog ( "option" , "title" , "Edit Note" )                 . load ( "/Home/Edit/" + id , function () { $ ( "#NoteDialog" ). dialog ( "open" ); });         });         $ ( ".AddLink" ). click ( function () {             $ ( "#NoteDialog" ). html ( "" )                 . dialog ( "option" , "title" , "Add Note" )                 . load ( "/Home/Create" , function () { $ ( "#NoteDialog" ). dialog ( "open" ); });         });         LoadList ();     });     function LoadList () {         $ ( "#NoteListBlock" ). load ( "/Home/List" );     } < /script> The <div> tag with the id attribute of "NoteListBlock" is used as a container target for the load of the partial view content of our List action method. It starts out empty and will get loaded with content via jQuery once the DOM is loaded. The <div> tag with the id attribute of "NoteDialog" is the element for our dialog widget. The jQuery UI library will use the title attribute for the text in the dialog widget top header bar. We start out with it empty here and will dynamically change the text via jQuery based on the request to either add or edit a note. This <div> tag is given a CSS class named "Hidden" that will set the display:none style on the element. Since our call to the jQuery UI method to make the element a dialog widget will occur in the jQuery document ready code block, the end user will see the <div> element rendered in their browser as the page renders and then it will hide after that jQuery call. Adding the display:hidden to the <div> element via CSS will ensure that it is never rendered until the user triggers the request to open the dialog. The jQuery document load block contains the setup for the dialog node, click event bindings for the edit and add links, and a call to a JavaScript function called LoadList that handles the AJAX call to the List action method. The .dialog() method is called on the "NoteDialog" <div> element and the options are set for the dialog widget. The buttons option defines 2 buttons and their click actions. The first is the "Save" button (the text in quotations is used as the text for the button) that will do an AJAX post to our Save action method and send the serialized form data from the note form (targeted with the id attribute "NoteForm"). Upon completion it will close the dialog widget and call the LoadList to update the UX without a redirect. The "Cancel" button simply closes the dialog widget. The .live() method handles binding a function to the "click" event on all elements with the CSS class named EditLink . We use the .live() method because it will catch and bind our function to elements even as the DOM changes. Since we will be constantly changing the note list as we add and edit we want to ensure that the edit links get wired up with click events. The function for the click event on the edit links gets the noteid attribute and stores it in a local variable. Then it clears out the HTML in the dialog element (to ensure a fresh start), calls the .dialog() method and sets the "title" option (this sets the title attribute value), and then calls the .load() AJAX method to hit our Edit action method and inject the returned content into the "NoteDialog" <div> element. Once the .load() method is complete it opens the dialog widget. The click event binding for the add link is similar to the edit, only we don't need to get the id value and we load the Create action method. This binding is done via the .click() method because it will only be bound on the initial load of the page. The add button will always exist. Finally, we toss in some CSS in the Content/Site.css file to style our form and the add/edit links. . ButtonLink { color : Blue ; cursor : pointer ; } . ButtonLink : hover { text - decoration : underline ; } . Hidden { display : none ; } #NoteForm label { display:block; margin-bottom:6px; } #NoteForm label > span { font-weight:bold; } #NoteForm input[type=text] { width:350px; } #NoteForm textarea { width:350px; height:80px; } With all of our code in place we can do an F5 and see our list of notes: If we click on an edit link we will get the dialog widget with the correct note data loaded: And if we click on the add new note link we will get the dialog widget with the empty form: The end result of our solution tree for our sample:

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• Only draw visible objects to the camera in 2D

  - by Deukalion

  I have Map, each map has an array of Ground, each Ground consists of an array of VertexPositionTexture and a texture name reference so it renders a texture at these points (as a shape through triangulation). Now when I render my map I only want to get a list of all objects that are visible in the camera. (So I won't loop through more than I have to) Structs: public struct Map { public Ground[] Ground { get; set; } } public struct Ground { public int[] Indexes { get; set; } public VertexPositionNormalTexture[] Points { get; set; } public Vector3 TopLeft { get; set; } public Vector3 TopRight { get; set; } public Vector3 BottomLeft { get; set; } public Vector3 BottomRight { get; set; } } public struct RenderBoundaries<T> { public BoundingBox Box; public T Items; } when I load a map: foreach (Ground ground in CurrentMap.Ground) { Boundaries.Add(new RenderBoundaries<Ground>() { Box = BoundingBox.CreateFromPoints(new Vector3[] { ground.TopLeft, ground.TopRight, ground.BottomLeft, ground.BottomRight }), Items = ground }); } TopLeft, TopRight, BottomLeft, BottomRight are simply the locations of each corner that the shape make. A rectangle. When I try to loop through only the objects that are visible I do this in my Draw method: public int Draw(GraphicsDevice device, ICamera camera) { BoundingFrustum frustum = new BoundingFrustum(camera.View * camera.Projection); // Visible count int count = 0; EffectTexture.World = camera.World; EffectTexture.View = camera.View; EffectTexture.Projection = camera.Projection; foreach (EffectPass pass in EffectTexture.CurrentTechnique.Passes) { pass.Apply(); foreach (RenderBoundaries<Ground> render in Boundaries.Where(m => frustum.Contains(m.Box) != ContainmentType.Disjoint)) { // Draw ground count++; } } return count; } When I try adding just one ground, then moving the camera so the ground is out of frame it still returns 1 which means it still gets draw even though it's not within the camera's view. Am I doing something or wrong or can it be because of my Camera? Any ideas why it doesn't work?

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• Top down space game control problem

  - by Phil

  As the title suggests I'm developing a top down space game. I'm not looking to use newtonian physics with the player controlled ship. I'm trying to achieve a control scheme somewhat similar to that of FlatSpace 2 (awesome game). I can't figure out how to achieve this feeling with keyboard controls as opposed to mouse controls though. Any suggestions? I'm using Unity3d and C# or javaScript (unityScript or whatever is the correct term) works fine if you want to drop some code examples. Edit: Of course I should describe FlatSpace 2's control scheme, sorry. You hold the mouse button down and move the mouse in the direction you want the ship to move in. But it's not the controls I don't know how to do but rather the feeling of a mix of driving a car and flying an aircraft. It's really well made. Youtube link: FlatSpace2 on iPhone I'm not developing an iPhone game but the video shows the principle of the movement style. Edit 2 As there seems to be a slight interest, I'll post the version of the code I've used to continue. It works good enough. Sometimes good enough is sufficient! using UnityEngine; using System.Collections; public class ShipMovement : MonoBehaviour { public float directionModifier; float shipRotationAngle; public float shipRotationSpeed = 0; public double thrustModifier; public double accelerationModifier; public double shipBaseAcceleration = 0; public Vector2 directionVector; public Vector2 accelerationVector = new Vector2(0,0); public Vector2 frictionVector = new Vector2(0,0); public int shipFriction = 0; public Vector2 shipSpeedVector; public Vector2 shipPositionVector; public Vector2 speedCap = new Vector2(0,0); void Update() { directionModifier = -Input.GetAxis("Horizontal"); shipRotationAngle += ( shipRotationSpeed * directionModifier ) * Time.deltaTime; thrustModifier = Input.GetAxis("Vertical"); accelerationModifier = ( ( shipBaseAcceleration * thrustModifier ) ) * Time.deltaTime; directionVector = new Vector2( Mathf.Cos(shipRotationAngle ), Mathf.Sin(shipRotationAngle) ); //accelerationVector = Vector2(directionVector.x * System.Convert.ToDouble(accelerationModifier), directionVector.y * System.Convert.ToDouble(accelerationModifier)); accelerationVector.x = directionVector.x * (float)accelerationModifier; accelerationVector.y = directionVector.y * (float)accelerationModifier; // Set friction based on how "floaty" controls you want shipSpeedVector.x *= 0.9f; //Use a variable here shipSpeedVector.y *= 0.9f; //<-- as well shipSpeedVector += accelerationVector; shipPositionVector += shipSpeedVector; gameObject.transform.position = new Vector3(shipPositionVector.x, 0, shipPositionVector.y); } }

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• What does template<class key, class type> mean before a method in C++?

  - by zengr

  Hi, I have got this code and I am trying to understand the convention followed, all the method defined in the .cpp file have template<class KeyType, class DataType> written before them. What does that mean? Example: //Constructor template<class key, class type> MyOperation<key, type>::MyOperation() { //method implementation } //A method template<class key, class type> MyOperation<key, type>::otherOperation() { //method implementation } Thanks

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• Java: omitting a data member from the equals method.

  - by cchampion

  public class GamePiece { public GamePiece(char cLetter, int nPointValue) { m_cLetter=cLetter; m_nPointValue=nPointValue; m_nTurnPlaced=0; //has not been placed on game board yet. } public char GetLetter() {return m_cLetter;} public int GetPointValue() {return m_nPointValue;} public int GetTurnPlaced() {return m_nTurnPlaced;} public void SetTurnPlaced(int nTurnPlaced) { m_nTurnPlaced=nTurnPlaced; } @Override public boolean equals(Object obj) { /*NOTE to keep this shorter I omitted some of the null checking and instanceof stuff. */ GamePiece other = (GamePiece) obj; //not case sensitive, and I don`t think we want it to be here. if(m_cLetter != other.m_cLetter) { return false; } if(m_nPointValue != other.m_nPointValue) { return false; } /* NOTICE! m_nPointValue purposely omitted. It does not affect hashcode or equals */ return true; } @Override public int hashCode() { /* NOTICE! m_nPointValue purposely omitted. It should not affect hashcode or equals */ final int prime = 41; return prime * (prime + m_nPointValue + m_cLetter); } private char m_cLetter; private int m_nPointValue; private int m_nTurnPlaced;//turn which the game piece was placed on the game board. Does not affect equals or has code! } Consider the given piece of code. This object has been immutable until the introduction of the m_nTurnPlaced member (which can be modified by the SetTurnPlaced method, so now GamePiece becomes mutable). GamePiece is used in an ArrayList, I call contains and remove methods which both rely on the equals method to be implemented. My question is this, is it ok or common practice in Java for some members to not affect equals and hashcode? How will this affect its use in my ArrayList? What type of java Collections would it NOT be safe to use this object now that it is mutable? I've been told that you're not supposed to override equals on mutable objects because it causes some collections to behave "strangely" (I read that somewhere in the java documentation).

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• Accessing non-static combbox property in the static method.

  - by Harikrishna

  I have one combobox on the window form and I have one method which is declared with static like private static DataTable ParseTable(HtmlNode table) Now I want to use combobox in that method for using combobox property but I can not access any property of combobox or combobox itself.If I made the combobox declaration as static then it can be accessed in that static method.But any alternative way to access combbox property in that static method because I don't want to make combobox declaration as static.

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