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  • When are predicates appropriate and what is the best pattern for usage

    - by Maxim Gershkovich
    When are predicates appropriate and what is the best pattern for usage? What are the advantages of predicates? It seems to me like most cases where a predicate can be employed a tight loop would accomplish the same functionality? I don’t see a reusability argument given you will probably only implement a predicate in one method right? They look and feel nice but besides that they seem like you would only employ them when you need a quick hack on the collection classes? UPDATE But why would you be rewriting the tight loop again and again? In my mind/code when it comes to collections I always end up with something like Class Person End Class Class PersonList Inherits List(Of Person) Function FindByName(Name) as Person tight loop.... End Function End Class @Ani By that same logic I could implement the method as such Class PersonList Inherits List(Of Person) Function FindByName(Name) as PersonList End Function Function FindByAge(Age) as PersonList End Function Function FindBySocialSecurityNumber(SocialSecurityNumber) as PersonList End Function End Class And call it as such Dim res as PersonList = MyList.FindByName("Max").FindByAge(25).FindBySocialSecurityNumber(1234) and the result along with the amount of code and its reusability is largely the same, no? I am not arguing just trying to understand.

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  • LINQ to SQL - Grouping categories by parentId

    - by creativeincode
    I am trying to construct a navigation menu using a Categories table from my db. I have a similar layout as below in Categories table. public List<Category> CategoryData = new List(new Category[] { new Category{ CategoryId = 1, Name = "Fruit", ParentCategoryId = null}, new Category{ CategoryId = 2, Name = "Vegetables", ParentCategoryId = null}, new Category{ CategoryId = 3, Name = "Apples", ParentCategoryId = 1}, new Category{ CategoryId = 4, Name = "Bananas", ParentCategoryId = 1}, new Category{ CategoryId = 5, Name = "Cucumber", ParentCategoryId = 2}, new Category{ CategoryId = 6, Name = "Onions", ParentCategoryId = 2} ); } The above should return something like Fruit (parent) "===Apples, Bananas (child) Vegetables (parent) "===Cucumber, Onions (child) I need to be able to pass this as some kind of 'grouped' (grouped by parentid) collection to my View. How to do this?

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  • Multi-tier applications using L2S, WCF and Base Class

    - by Gena Verdel
    Hi all. One day I decided to build this nice multi-tier application using L2S and WCF. The simplified model is : DataBase-L2S-Wrapper(DTO)-Client Application. The communication between Client and Database is achieved by using Data Transfer Objects which contain entity objects as their properties. abstract public class BaseObject { public virtual IccSystem.iccObjectTypes ObjectICC_Type { get { return IccSystem.iccObjectTypes.unknownType; } } [global::System.Data.Linq.Mapping.ColumnAttribute(Storage = "_ID", AutoSync = AutoSync.OnInsert, DbType = "BigInt NOT NULL IDENTITY", IsPrimaryKey = true, IsDbGenerated = true)] [global::System.Runtime.Serialization.DataMemberAttribute(Order = 1)] public virtual long ID { //get; //set; get { return _ID; } set { _ID = value; } } } [DataContract] public class BaseObjectWrapper<T> where T : BaseObject { #region Fields private T _DBObject; #endregion #region Properties [DataMember] public T Entity { get { return _DBObject; } set { _DBObject = value; } } #endregion } Pretty simple, isn't it?. Here's the catch. Each one of the mapped classes contains ID property itself so I decided to override it like this [global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.Divisions")] [global::System.Runtime.Serialization.DataContractAttribute()] public partial class Division : INotifyPropertyChanging, INotifyPropertyChanged { [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_ID", AutoSync=AutoSync.OnInsert, DbType="BigInt NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)] [global::System.Runtime.Serialization.DataMemberAttribute(Order=1)] public override long ID { get { return this._ID; } set { if ((this._ID != value)) { this.OnIDChanging(value); this.SendPropertyChanging(); this._ID = value; this.SendPropertyChanged("ID"); this.OnIDChanged(); } } } } Wrapper for division is pretty straightforward as well: public class DivisionWrapper : BaseObjectWrapper<Division> { } It worked pretty well as long as I kept ID values at mapped class and its BaseObject class the same(that's not very good approach, I know, but still) but then this happened: private CentralDC _dc; public bool UpdateDivision(ref DivisionWrapper division) { DivisionWrapper tempWrapper = division; if (division.Entity == null) { return false; } try { Table<Division> table = _dc.Divisions; var q = table.Where(o => o.ID == tempWrapper.Entity.ID); if (q.Count() == 0) { division.Entity._errorMessage = "Unable to locate entity with id " + division.Entity.ID.ToString(); return false; } var realEntity = q.First(); realEntity = division.Entity; _dc.SubmitChanges(); return true; } catch (Exception ex) { division.Entity._errorMessage = ex.Message; return false; } } When trying to enumerate over the in-memory query the following exception occurred: Class member BaseObject.ID is unmapped. Although I'm stating the type and overriding the ID property L2S fails to work. Any suggestions?

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  • Find the right parameters for an event without using Design Mode in Visual Studio 2010

    - by Jason
    Is there a way to know what parameters are needed by an event in Visual Studio 2010? Let's say I have a DropDownList control and I want to bind a method to the "OnSelectedIndexChanged", I would do something like this In the ASPX File: <asp:DropDownList ID="lstMyList" runat="server" OnSelectedIndexChanged="lstMyList_SelectedIndexChanged"></asp:DropDownList> In the codebehind: protected void lstMyList_SelectedIndexChanged(object sender, EventArgs e) { ... } Is there a way to know what parameters the method needs? (In this case, an object for the sender and an EventArgs parameter for the event.) I know you can easily create the method by double-clicking the right event in Design Mode, but it does a mess with your code so I prefer not to use it. Thanks!

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  • Get The Currency From Current Culture?

    - by leen3o
    Is there a way to get current information dynamically from the apps culture settings? Basically if the user has set the culture to US I want to know the currency is dollars, or if they have it set to UK I want to pound sterling etc... etc.. This is so I can send this information to PayPal when a payment is being made

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  • Why is TRest in Tuple<T1... TRest> not constrained?

    - by Anthony Pegram
    In a Tuple, if you have more than 7 items, you can provide an 8th item that is another tuple and define up to 7 items, and then another tuple as the 8th and on and on down the line. However, there is no constraint on the 8th item at compile time. For example, this is legal code for the compiler: var tuple = new Tuple<int, int, int, int, int, int, int, double> (1, 1, 1, 1, 1, 1, 1, 1d); Even though the intellisense documentation says that TRest must be a Tuple. You do not get any error when writing or building the code, it does not manifest until runtime in the form of an ArgumentException. You can roughly implement a Tuple in a few minutes, complete with a Tuple-constrained 8th item. I just wonder why it was left off the current implementation? Is it possibly a forward-compatibility issue where they could add more elements with a hypothetical C# 5? Short version of rough implementation interface IMyTuple { } class MyTuple<T1> : IMyTuple { public T1 Item1 { get; private set; } public MyTuple(T1 item1) { Item1 = item1; } } class MyTuple<T1, T2> : MyTuple<T1> { public T2 Item2 { get; private set; } public MyTuple(T1 item1, T2 item2) : base(item1) { Item2 = item2; } } class MyTuple<T1, T2, TRest> : MyTuple<T1, T2> where TRest : IMyTuple { public TRest Rest { get; private set; } public MyTuple(T1 item1, T2 item2, TRest rest) : base(item1, item2) { Rest = rest; } } ... var mytuple = new MyTuple<int, int, MyTuple<int>>(1, 1, new MyTuple<int>(1)); // legal var mytuple2 = new MyTuple<int, int, int>(1, 2, 3); // illegal

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  • when i merge a data table with a typed dataset, one single field on a single row is DBNull sometimes

    - by benj007
    Hi everybody, I have a strange problem sometimes when I try to merge a data table with a typed dataset my data table is filled in with a stored procedure and when I checked the content of this table it is ok, everything is in there straight after I merge it with my core typed dataset like this : MyTypedDataSet.TheTable.Clear(); MyTypedDataSet.TheTable.Merge(MyDataTable); and now if i check the table in the dataset everything is ok except only one single field on one single row which is DBNull, that makes no sense because the source data table contains the good integer vaue. Thanks a lot in advance guys :)

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  • Does collections type conversion util methods already exist in any API?

    - by Delta
    interface TypeConverter<T, E> { T convert(E e); } class CollectionUtil() { public static <E> List<T> convertToList(List<E> fromList, TypeConverter<T, E> conv) { { if(fromList== null) return null; List<T> newList = new ArrayList<T>(fromList.size()) for(E e : fromList) { newList.add(conv.convert(e)); } return newList; } } Above code explains converting from List of String to List of Integer by implementing TypeConverter interface for String, Integer. Are there already any collections conversion utility methods exists in any API like list to set and so on?

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  • Creating a Type object corresponding to a generic type

    - by Alexey Romanov
    In Java, how can I construct a Type object for Map<String, String>? System.out.println(Map<String, String>.class); doesn't compile. One workaround I can think of is private Map<String, String> dummy() { throw new Error(); } Type mapStringString = Class.forName("ThisClass").getMethod("dummy", null).getGenericReturnType(); Is this the correct way?

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  • im unable to validate a login of users ,since if im entering the wrong values my datareader is not getting executed y ?

    - by Salman_Khan
    //code private void glassButton1_Click(object sender, EventArgs e) { if (textBox1.Text == "" || textBox1.Text == "" || comboBox1.SelectedIndex == 0) { Message m = new Message(); m.ShowDialog(); } else { try { con.ConnectionString = "Data source=BLACK-PEARL;Initial Catalog=LIFELINE ;User id =sa; password=143"; con.Open(); SqlCommand cmd = new SqlCommand("Select LoginID,Password,Department from Login where LoginID=@loginID and Password=@Password and Department=@Department", con); cmd.Parameters.Add(new SqlParameter("@loginID", textBox1.Text)); cmd.Parameters.Add(new SqlParameter("@Password", textBox2.Text)); cmd.Parameters.Add(new SqlParameter("@Department", comboBox1.Text)); SqlDataReader dr = cmd.ExecuteReader(); if (dr.Read()) { string Strname = dr[0].ToString(); string StrPass = dr[1].ToString(); string StrDept = dr[2].ToString(); if(dr[2].ToString().Equals(comboBox1.Text)&&dr[0].ToString().Equals(textBox1.Text)&&dr[1].ToString().Equals(textBox2.Text)) { MessageBox.Show("Welcome"); } else { MessageBox.Show("Please Enter correct details"); } } dr.Close(); } catch (Exception ex) { MessageBox.Show("Exception" + ex); } finally { con.Close(); } } }

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  • ASP MVC: E-mail Verification (Encrypting the activation link)

    - by wh0emPah
    Okay i'm a little bit stuck on how to solve this problem. When a user registers. I want to send him a link so that he can verify hes email address. But i have troubles generating the link. I've already written the controller to accept the links with the correct keys. i only have no idea on how to generate the activation keys. So when the user registers i'll send him a link by mail like this: Your activation link is : http://site.com/user/verify?key=keyhere Now i have created this method (called by the controller/action) to handle the key in the link: public string Verify(string value) { String email = Decrypt(value); user u = gebRep.GetUsers().WithEmail(email).SingleOrDefault(); if (u != null) { u.emailValid = true; userReppository.Save(); } return "Invallid validation value!"; } Now my problem is I have no idea on how to encrypt and decrypt the email into some sort of key (url friendly) So i can mail it with the link and can use it to verify the email. I need some kind of (not to complicated but secure) way to encrypt the email into a urlfriendly key. Tyvm

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  • html.actionlink doesn't passing parameter to controller action

    - by FosterZ
    hi, m having problem in passing parameter to controller action, i have done the following Url.Action("SchoolDetails","School",new{id=item.SchoolId}) and my controller action follows public ActionResult SchoolDetails(string schoolId,_ASI_School schoolDetail) { schoolDetail = SchoolRepository.GetSchoolById(schoolId); return View(schoolDetail); } i dn't know why the schoolId above in action is getting null..

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  • Java: how do I get a class literal from a generic type?

    - by Tom
    Typically, I've seen people use the class literal like this: Class<Foo> cls = Foo.class; But what if the type is generic, e.g. List? This works fine, but has a warning since List should be parameterized: Class<List> cls = List.class So why not add a <?>? Well, this causes a type mismatch error: Class<List<?>> cls = List.class I figured something like this would work, but this is just a plain ol' a syntax error: Class<List<Foo>> cls = List<Foo>.class How can I get a Class<List<Foo>> statically, e.g. using the class literal? I could use @SuppressWarnings("unchecked") to get rid of the warnings caused by the non-parameterized use of List in the first example, Class<List> cls = List.class, but I'd rather not. Any suggestions? Thanks!

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  • Using the same code in different (partial) views

    - by Danny Chen
    Maybe this question is quite simple because I'm new to MVC2. I have a simple demo MVC project. (1) A weak-typed view: Index.aspx <% Html.RenderPartial("ArticalList", ViewData["AllArticals"] as List<Artical>); %> (2) A strong-typed partical view: ArticalList.ascx <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl<List<Artical>>" %> <% foreach (Artical a in Model) { %> <%= Html.ActionLink(a.Title, "About", new { id = a.ID })%><br /> <%} %> (3) Here is the HomeController.cs public ActionResult Index() { ViewData["AllArticals"] = Artical.GetArticals(); return View(); } public ActionResult ArticalList() { return PartialView(Artical.GetArticals()); } Sorry I'm using a Web-Form "angle", because if I'm using a Web-Form, when I visit Index.aspx, rendering ArticalList.ascx will call public ActionResult ArticalList(). But here I need to write Artical.GetArticals() twice in two actions. How can I put them in one?

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  • Using reflection to find all linq2sql tables and ensure they match the database

    - by Jake Stevenson
    I'm trying to use reflection to automatically test that all my linq2sql entities match the test database. I thought I'd do this by getting all the classes that inherit from DataContext from my assembly: var contexttypes = Assembly.GetAssembly(typeof (BaseRepository<,>)).GetTypes().Where( t => t.IsSubclassOf(typeof(DataContext))); foreach (var contexttype in contexttypes) { var context = Activator.CreateInstance(contexttype); var tableProperties = type.GetProperties().Where(t=> t.PropertyType.Name == typeof(ITable<>).Name); foreach (var propertyInfo in tableProperties) { var table = (propertyInfo.GetValue(context, null)); } } So far so good, this loops through each ITable< in each datacontext in the project. If I debug the code, "table" is properly instantiated, and if I expand the results view in the debugger I can see actual data. BUT, I can't figure out how to get my code to actually query that table. I'd really like to just be able to do table.FirstOrDefault() to get the top row out of each table and make sure the SQL fetch doesn't fail. But I cant cast that table to be anything I can query. Any suggestions on how I can make this queryable? Just the ability to call .Count() would be enough for me to ensure the entities don't have anything that doesn't match the table columns.

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  • Nullable<T> as a parameter

    - by ferch
    I alredy have this: public static object GetDBValue(object ObjectEvaluated) { if (ObjectEvaluated == null) return DBNull.Value; else return ObjectEvaluated; } used like: List<SqlParameter> Params = new List<SqlParameter>(); Params.Add(new SqlParameter("@EntityType", GetDBValue(EntityType))); Now i wanted to keep the same interface but extend that to use it with nullable public static object GetDBValue(int? ObjectEvaluated) { if (ObjectEvaluated.HasValue) return ObjectEvaluated.Value; else return DBNull.Value; } public static object GetDBValue(DateTime? ObjectEvaluated) {...} but i want only 1 function GetDBValue for nullables. How do I do that and keep the call as is is? Is that possible at all? I can make it work like: public static object GetDBValue<T>(Nullable<T> ObjectEvaluated) where T : struct { if (ObjectEvaluated.HasValue) return ObjectEvaluated.Value; else return DBNull.Value; } But the call changes to: Params.Add(new SqlParameter("@EntityID ", GetDBValue<int>(EntityID)));

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  • Binding an Ilist to datagridview containing another object in a field

    - by JaSk
    I have pretty much the same problem as this question http://stackoverflow.com/questions/970741 but in windows forms, can anyone help me solve it? this is my code, so you don't have to check the other question: public class Material { public virtual int id { get; private set; } public virtual string nombre { get; set; } public virtual string unidad { get; set; } public virtual Categorias Categoria { get; set; } public virtual IList Materiales { get; set; } public Material() { Materiales = new List<Materiales>(); } public virtual void AddMateriales(Materiales materiales) { materiales.Material = this; this.Materiales.Add(materiales); } } as you can see I have an object within the IList so when I use the List as the data source for a datagridview I get a object.categoria where I want to get the Categoria.Name property, can anyone help me?. Thanks

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  • Why is Func<T> ambiguous with Func<IEnumerable<T>>?

    - by Matt Hamilton
    This one's got me flummoxed, so I thought I'd ask here in the hope that a C# guru can explain it to me. Why does this code generate an error? class Program { static void Main(string[] args) { Foo(X); // the error is on this line } static String X() { return "Test"; } static void Foo(Func<IEnumerable<String>> x) { } static void Foo(Func<String> x) { } } The error in question: Error 1 The call is ambiguous between the following methods or properties: 'ConsoleApplication1.Program.Foo(System.Func<System.Collections.Generic.IEnumerable<string>>)' and 'ConsoleApplication1.Program.Foo(System.Func<string>)' C:\Users\mabster\AppData\Local\Temporary Projects\ConsoleApplication1\Program.cs 12 13 ConsoleApplication1 It doesn't matter what type I use - if you replace the "String" declarations with "int" in that code you'll get the same sort of error. It's like the compiler can't tell the difference between Func<T> and Func<IEnumerable<T>>. Can someone shed some light on this?

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  • Replace {tag} with a value or completely remove {any-tag}

    - by HasanGursoy
    I've designed a multilingual web site and some values in database have a tag which will be replaced with it's language value, remove tags brackets ( in case {} ) or removed completely. There are two cases: Remove brackets: value {mm} >> value mm Remove completely: value {mm} >> value Also {tag} could be any length and can contain - Can anybody help me with regex?

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  • Existentials and Scrap your Boilerplate

    - by finnsson
    I'm writing a XML (de)serializer using Text.XML.Light and Scrap your Boilerplate (at http://github.com/finnsson/Text.XML.Generic) and so far I got working code for "normal" ADTs but I'm stuck at deserializing existentials. I got the existential data type data DataBox where DataBox :: (Show d, Eq d, Data d) => d -> DataBox and I'm trying to get this to compile instance Data DataBox where gfoldl k z (DataBox d) = z DataBox `k` d gunfold k z c = k (z DataBox) -- not OK toConstr (DataBox d) = toConstr d dataTypeOf (DataBox d) = dataTypeOf d but I can't figure out how to implement gunfold for DataBox. The error message is Text/XML/Generic.hs:274:23: Ambiguous type variable `b' in the constraints: `Eq b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Show b' arising from a use of `DataBox' at Text/XML/Generic.hs:274:23-29 `Data b' arising from a use of `k' at Text/XML/Generic.hs:274:18-30 Probable fix: add a type signature that fixes these type variable(s) It's complaining about not being able to figure out the data type of b. I'm also trying to implement dataCast1 and dataCast2 but I think I can live without them (i.e. an incorrect implementation). I guess my questions are: Is it possible to combine existentials with Scrap your Boilerplate? If so: how do you implement gunfold for an existential data type?

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  • Can't sent xml file from Web Application on Internet Explorer

    - by nCdy
    Error is something like that : Can't load Items.aspx from 192.168.0.172 And a text is Can't open this web-site. It can't be found. Try later code : HttpContext.Current.Response.Clear(); HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache); HttpContext.Current.Response.Charset = System.Text.Encoding.Unicode.EncodingName; HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.Unicode; HttpContext.Current.Response.BinaryWrite(System.Text.Encoding.Unicode.GetPreamble()); HttpContext.Current.Response.ContentType = "application/vnd.ms-excel"; HttpContext.Current.Response.AddHeader( "content-disposition", string.Format( "attachment; filename={0}",fileName)); .... table.RenderControl(htw); HttpContext.Current.Response.Write(sw.ToString()); HttpContext.Current.Response.End(); Trouble with this file is only for Internet Explorer (works on opera / firefox ... ) And so it works for HTML with no HttpContext.Current.Response.ContentType = "application/vnd.ms-excel"; this string

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  • DisplayName attribute from Resources?

    - by Palantir
    Hello! I have a localized application, and I am wondering if it is possible to have the DisplayName for a certain model property set from a Resource. I'd like to do something like this: public class MyModel { [Required] [DisplayName(Resources.Resources.labelForName)] public string name{ get; set; } } But I can't to it, as the compiler says: "An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type" :( Are there any workarounds? I am outputting labels manually, but I need these for the validator output!

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  • Winform Textbox CanGrow ?

    - by bochur1
    I don't find a CanGrow property on the Textbox control. This is common in some other controls, and what it does is expand the control to acomodate more data. Anyway to get this feature in the TextBox?

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