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  • C# Property Access vs Interface Implementation

    - by ehdv
    I'm writing a class to represent a Pivot Collection, the root object recognized by Pivot. A Collection has several attributes, a list of facet categories (each represented by a FacetCategory object) and a list of items (each represented by a PivotItem object). Therefore, an extremely simplified Collection reads: public class Collection { private List<FacetCategory> categories; private List<PivotItem> items; // other attributes } What I'm unsure of is how to properly grant access to those two lists. Because declaration order of both facet categories and items is visible to the user, I can't use sets, but the class also shouldn't allow duplicate categories or items. Furthermore, I'd like to make the Collection object as easy to use as possible. So my choices are: Have Collection implement IList<PivotItem> and have accessor methods for FacetCategory: In this case, one would add an item to Collection foo by writing foo.Add(bar). This works, but since a Collection is equally both kinds of list making it only pass as a list for one type (category or item) seems like a subpar solution. Create nested wrapper classes for List (CategoryList and ItemList). This has the advantage of making a consistent interface but the downside is that these properties would no longer be able to serve as lists (because I need to override the non-virtual Add method I have to implement IList rather than subclass List. Implicit casting wouldn't work because that would return the Add method to its normal behavior. Also, for reasons I can't figure out, IList is missing an AddRange method... public class Collection { private class CategoryList: IList<FacetCategory> { // ... } private readonly CategoryList categories = new CategoryList(); private readonly ItemList items = new ItemList(); public CategoryList FacetCategories { get { return categories; } set { categories.Clear(); categories.AddRange(value); } } public ItemList Items { get { return items; } set { items.Clear(); items.AddRange(value); } } } Finally, the third option is to combine options one and two, so that Collection implements IList<PivotItem> and has a property FacetCategories. Question: Which of these three is most appropriate, and why?

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  • Best practices regarding equals: to overload or not to overload?

    - by polygenelubricants
    Consider the following snippet: import java.util.*; public class EqualsOverload { public static void main(String[] args) { class Thing { final int x; Thing(int x) { this.x = x; } public int hashCode() { return x; } public boolean equals(Thing other) { return this.x == other.x; } } List<Thing> myThings = Arrays.asList(new Thing(42)); System.out.println(myThings.contains(new Thing(42))); // prints "false" } } Note that contains returns false!!! We seems to have lost our things!! The bug, of course, is the fact that we've accidentally overloaded, instead of overridden, Object.equals(Object). If we had written class Thing as follows instead, then contains returns true as expected. class Thing { final int x; Thing(int x) { this.x = x; } public int hashCode() { return x; } @Override public boolean equals(Object o) { return (o instanceof Thing) && (this.x == ((Thing) o).x); } } Effective Java 2nd Edition, Item 36: Consistently use the Override annotation, uses essentially the same argument to recommend that @Override should be used consistently. This advice is good, of course, for if we had tried to declare @Override equals(Thing other) in the first snippet, our friendly little compiler would immediately point out our silly little mistake, since it's an overload, not an override. What the book doesn't specifically cover, however, is whether overloading equals is a good idea to begin with. Essentially, there are 3 situations: Overload only, no override -- ALMOST CERTAINLY WRONG! This is essentially the first snippet above Override only (no overload) -- one way to fix This is essentially the second snippet above Overload and override combo -- another way to fix The 3rd situation is illustrated by the following snippet: class Thing { final int x; Thing(int x) { this.x = x; } public int hashCode() { return x; } public boolean equals(Thing other) { return this.x == other.x; } @Override public boolean equals(Object o) { return (o instanceof Thing) && (this.equals((Thing) o)); } } Here, even though we now have 2 equals method, there is still one equality logic, and it's located in the overload. The @Override simply delegates to the overload. So the questions are: What are the pros and cons of "override only" vs "overload & override combo"? Is there a justification for overloading equals, or is this almost certainly a bad practice?

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  • java Database framework comparison

    - by user293655
    Hi, I want to create an application that synchronize a database to multiple databases(various type of databases). I'm looking for a framework that suitable to do this. I was looking for something just get the Object of the data (like a resultset) then copy that object to the destination database. Or comparing between 2 data. Any ideas? Thanks,

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  • What's the proper and reliable way to store an XML string as a JSON property?

    - by Edwin
    Hi Folks, I want to store a string which itself is an XML string as a property of an JSON object , what's the reliable and proper way of dong this? Should I first encode the XML data into BASE64 first prior saving it to an JSON object, due to the fact that JSON does not support binary data? Example of data I want to store: { "string1" : "...moderately complex XML..." } Thank you in advance for any hints and suggestions!

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  • Combine hash values in C#

    - by Chris
    I'm creating a generic object collection class and need to implement a Hash function. I can obviously (and easily!) get the hash values for each object but was looking for the 'correct' way to combine them to avoid any issues. Does just adding, xoring or any basic operation harm the quality of the hash or am I going to have to do something like getting the objects as bytes, combining them and then hashing that? Cheers in advance

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  • Jquery $().each method obscures 'this' keyword

    - by Jeff Fritz
    I am creating a Javascript object that contains a function that executes a jQuery each method like the following: function MyClass { Method1 = function(obj) { // Does something here } Method2 = function() { $(".SomeClass").each(function() { // 1 2 this.Method1(this); }); } } Which object is each THIS referring to? jQuery is referring to the item returned from the each iteration. However, I would like This[1] to refer to the containing class... How can I refer to the containing class from within the jQuery loop?

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  • ASP.NET Application Level vs. Session Level and Global.asax...confused

    - by contactmatt
    The following text is from the book I'm reading, 'MCTS Self-Paced Training Kit (Exam 70-515) Web Applications Development with ASP.NET 4". It gives the rundown of the Application Life Cycle. A user first makes a request for a page in your site. The request is routed to the processing pipeline, which forwards it to the ASP.NET runtime. The ASP.NET runtime creates an instance of the ApplicationManager class; this class instance represents the .NET framework domain that will be used to execute requests for your application. An application domain isolates global variables from other applications and allows each application to load and unload separately, as required. After the application domain has been created, an instance of the HostingEnvironment class is created. This class provides access to items inside the hosting environment, such as directory folders. ASP.NET creates instances of the core objects that will be used to process the request. This includes HttpContext, HttpRequest, and HttpResponse objects. ASP.NET creates an instance of the HttpApplication class (or an instance is reused). This class is also the base class for a site’s Global.asax file. You can use this class to trap events that happen when your application starts or stops. When ASP.NET creates an instance of HttpApplication, it also creates the modules configured for the application, such as the SessionStateModule. Finally, ASP.NET processes request through the HttpApplication pipleline. This pipeline also includes a set of events for validating requests, mapping URLs, accessing the cache, and more. The book then demonstrated an example of using the Global.asax file: <script runat="server"> void Application_Start(object sender, EventArgs e) { Application["UsersOnline"] = 0; } void Session_Start(object sender, EventArgs e) { Application.Lock(); Application["UsersOnline"] = (int)Application["UsersOnline"] + 1; Application.UnLock(); } void Session_End(object sender, EventArgs e) { Application.Lock(); Application["UsersOnline"] = (int)Application["UsersOnline"] - 1; Application.UnLock(); } </script> When does an application start? Whats the difference between session and application level? I'm rather confused on how this is managed. I thought that Application level classes "sat on top of" an AppDomain object, and the AppDomain contained information specific to that Session for that user. Could someone please explain how IIS manages Applicaiton level classes, and how an HttpApplication class sits under an AppDomain? Anything is appreciated.

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  • How to map an array to multiple properties using AutoMapper?

    - by Dror Helper
    I need to map a single fixed sized array array to multiple properties. For example given this class: public class Source { public int[] ItemArray{get;set} // always 4 items } I want to map the array to this class public class Dest { public int Item1{get;set;} public int Item1{get;set;} public int Item1{get;set;} public int Item1{get;set;} } Is there a simple way to do it with AutoMapper (without actually mapping each individual field)?

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  • store objects in $_GET

    - by mixm
    how can i store an object in the $_GET array in PHP. i want to pass an object containing database information from one page to another page via the $_GET array, so there would be no need to access the database again.

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  • Do Django Models inherit managers? (Mine seem not to)

    - by Zach
    I have 2 models: class A(Model): #Some Fields objects = ClassAManager() class B(A): #Some B-specific fields I would expect B.objects to give me access to an instance of ClassAManager, but this is not the case.... >>> A.objects <app.managers.ClassAManager object at 0x103f8f290> >>> B.objects <django.db.models.manager.Manager object at 0x103f94790> Why doesn't B inherit the objects attribute from A?

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  • Difference between library and native library

    - by Alvin
    Could anyone tell me the difference between library and native library in terms of java? I found the word "native library" in the following line: Type 1 - drivers that implement the JDBC API as a mapping to another data access API, such as ODBC. Drivers of this type are generally dependent on a native library, which limits their portability. The JDBC-ODBC Bridge driver is an example of a Type 1 driver. which you can found here

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  • Triangle rendering problem in directX

    - by Himadri
    I am working with directX 9. I have a problem while rendering triangles using drawprimitive. The problem is - When I am rendering the whole object made of several triangles, the triangle having all points on a single line shows gap in a whole closed object. I am showing the image below. The white dashed line is the problem.

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  • Axis Rotation Question

    - by Leo
    By using left hand rule, I rotate one object left and right using y axis, and rotate up/down using x axis. After first object is rotated to the right, the up/down rotation should be using z axis. However, when I try to rotate using z axis, after the first rotation, it has the same effect when I rotate using y axis. Anyone has any ideas? Thanks

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  • N2Cms, Adding a new property to a ContentPageBase class, corrupts the already entered data.

    - by Nour Sabouny
    i want to modify the ContentPageBase, in a functional site, i tried to add a property called for example (weight), but if there is an existing page in the database, the site will malfunction, and throws an Exception, of (Object reference not set to an instance of an object). how can i correct the already entered data ? public abstract class ContentPageBase : PageBase, ICommentable { [EditableTextBox("Weight", 10, ContainerName = Tabs.Details)] //newly added property. public virtual int Weight { get { return (int)GetDetail("Weight"); } set { SetDetail("Weight", value); } } }

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  • How does Java pick which method to call?

    - by Gaurav
    Given the following code: public class Test { public void method(Object o){ System.out.println("object"); } public void method(String s) { System.out.println("String"); } public void method() { System.out.println("blank"); } /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub Test test=new Test(); test.method(null); } } Java prints "String". Why is this the case?

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  • KeyDown Event is not responding till any user control is clicked or setFocus implicitly ?

    - by Subhen
    KeyDown Event is not responding till any user control is clicked or setFocus implicitly . I want to fire the key event after the page loads , anytime. I tried like : private void Page_KeyDown(object sender, KeyEventArgs e) { if (e.Key.ToString() == "Escape") { string uri = "/Views/Music/ArtistbyAlbum"; this.NavigationService.Navigate(new Uri(uri, UriKind.Relative)); } } void LayoutRoot_KeyDown(object sender, KeyEventArgs e) { MessageBox.Show("hi"); } Please help. Thanks, Subhen

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  • NHibernate unintentional lazy property loading

    - by chiccodoro
    I introduced a mapping for a business object which has (among others) a property called "Name": public class Foo : BusinessObjectBase { ... public virtual string Name { get; set; } } For some reason, when I fetch "Foo" objects, NHibernate seems to apply lazy property loading (for simple properties, not associations): The following code piece generates n+1 SQL statements, whereof the first only fetches the ids, and the remaining n fetch the Name for each record: ISession session = ...IQuery query = session.CreateQuery(queryString); ITransaction tx = session.BeginTransaction(); List<Foo> result = new List<Foo>(); foreach (Foo foo in query.Enumerable()) { result.Add(foo); } tx.Commit(); session.Close(); produces: NHibernate: select foo0_.FOO_ID as col_0_0_ from V1_FOO foo0_<br/> NHibernate: SELECT foo0_.FOO_ID as FOO1_2_0_, foo0_.NAME as NAME2_0_ FROM V1_FOO foo0_ WHERE foo0_.FOO_ID=:p0;:p0 = 81<br/> NHibernate: SELECT foo0_.FOO_ID as FOO1_2_0_, foo0_.NAME as NAME2_0_ FROM V1_FOO foo0_ WHERE foo0_.FOO_ID=:p0;:p0 = 36470<br/> NHibernate: SELECT foo0_.FOO_ID as FOO1_2_0_, foo0_.NAME as NAME2_0_ FROM V1_FOO foo0_ WHERE foo0_.FOO_ID=:p0;:p0 = 36473 Similarly, the following code leads to a LazyLoadingException after session is closed: ISession session = ... ITransaction tx = session.BeginTransaction(); Foo result = session.Load<Foo>(id); tx.Commit(); session.Close(); Console.WriteLine(result.Name); Following this post, "lazy properties ... is rarely an important feature to enable ... (and) in Hibernate 3, is disabled by default." So what am I doing wrong? I managed to work around the LazyLoadingException by doing a NHibernateUtil.Initialize(foo) but the even worse part are the n+1 sql statements which bring my application to its knees. This is how the mapping looks like: <class name="Foo" table="V1_FOO"> ... <property name="Name" column="NAME"/> </class> BTW: The abstract "BusinessObjectBase" base class encapsulates the ID property which serves as the internal identifier.

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  • How do I convert int? into int

    - by Richard77
    Hello, I've create a SPROC that saves an object and returns the id of the new object saved. Now, I'd like to return an int not an int? public int Save(Contact contact) { int? id; context.Save_And_SendBackID(contact.FirstName, contact.LastName, ref id); //How do I return an int instead of an int? } Thanks for helping

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  • Rollback SQL Server 2012 Sequence

    - by VAAA
    I have a SQL Server 2012 Sequence object: /****** Create Sequence Object ******/ CREATE SEQUENCE TestSeq START WITH 1 INCREMENT BY 1; I have a SP that runs some queries inside a transaction: BEGIN TRAN SELECT NEXT VALUE FOR dbo.TestSeq <here all the query update code......> ROLLBACK TRAN If the transaction fails all the updates are rolledback without problem but the Sequence is not rolled back I guess because Its out of the scope of the transaction. Any clue on way to handle that? Thanks

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  • ASP.NET MVC Default URL View

    - by Moose Factory
    I'm trying to set the Default URL of my MVC application to a view within an area of my application. The area is called "Common", the controller "Home" and the view "Index". I've tried setting the defaultUrl in the forms section of web.config to "~/Common/Home/Index" with no success. I've also tried mapping a new route in global.asax, thus: routes.MapRoute( "Area", "{area}/{controller}/{action}/{id}", new { area = "Common", controller = "Home", action = "Index", id = "" } ); Again, to no avail.

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