Type variance in .NET Framework 4.0
IEnumerable<T>, IComparable<T> and a few more are now type-variant. IList<T>, ICollection<T> and many others aren't. Why? ...
generics
Generic many-to-many relationships
I'm trying to create a messaging system where a message's sender and recipients can be generic entities. This seems fine for the sender, where there is only object to reference (GenericForeignKey) but I can't figure out how to go about this for the recipients (GenericManyToManyKey ??) Below is a simplified example. PersonClient and Comp...
Is there a clean way of referencing generic classes in a non-generic context?
Consider the following: public interface ICleanCoder { void DoSomeCoding(object task); } public interface ICleanCoder<T> { void DoSomeCoding(T task); } ... public class TestCleanCoding { void RegisterCleanCoder(ICleanCoder coder); } I have to have the initial non generic interface to enable a non generic reference to it...
What is truly wrong with Java generics?
Possible Duplicate: Why do some claim that Java's implementation of generics is bad? What's really so wrong with Java's generics? Or perhaps another way, what's so much better about other languages' implementations of similar concepts? I don't mean to spark any wars, but I haven't programmed in Java since 1.4 (i.e. before gene...
how to adjust "is a type but is used like a variable"?
i try to generate some codes in web service. But returing 2 error: 1) List is a type but is used like a variable 2) No overload for method 'Customer' takes '3 arguments' [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [ToolboxItem(false)] public class wstest :...
How to Bind List<myclass> data with gridview?
Look please my web service codes return type List i get data from web service with listformat List; also created a gridview below and return list to gridview datasource.Bur eror occurs: A field or property with the name 'name' was not found on the selected data source. <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns...
What's the difference between SortedList and SortedDictionary?
Maybe a silly question, but is there any real practical difference between a SortedList and a SortedDictionary? Are there any circumstances where you would specifically use one and not the other? ...
Java erasure error with unrelated generic in method
I've read the other questions related to erasures, but I'm still not clear why I get the compile error in the class below. The other questions involve methods that actually use the generic type, whereas I'm just trying to implement a method using the exact same signature. Can anyone explain? Compile error -> name clash: bar(java.util....
Static method in a generic class?
In Java, I'd like to have something as: class Clazz<T> { static void doIt(T object) { // shake that booty } } But I get Cannot make a static reference to the non-static type T I don't understand generics beyond the basic uses and thus can't make much sense of that. It doesn't help that I wasn't able to find much info on the ...
C#: Access SQL view through generic RepositoryBase class?
I'm using a RepositoryBase<T> base class as the foundation for my individual repositories (e.g. UserRepository). It simplifies things like adding new entities etc. for example: public IQueryable<T> SelectAll() { return db.GetTable<T>().AsQueryable<T>(); } Now I've added a view "UserActive" in my database. Is there any way to...
Reference generic property in expression
Let's say I have two Tables, Lunch and Dinner. I know that both contain the DateTime property "Time". If I have a generic method GetTime, how could I return db.Lunch.Time when T is Lunch and db.Dinner.Time when T is Dinner? I'm trying to achieve this without testing for T individually using typeof, but rather generically. Pseudocode: ...
PropertyInfo.GetValue() - how do you index into a generic parameter using reflection in C#?
This (shortened) code.. for (int i = 0; i < count; i++) { object obj = propertyInfo.GetValue(Tcurrent, new object[] { i }); } .. is throwing a 'TargetParameterCountException : Parameter count mismatch' exception. The underlying type of 'propertyInfo' is a Collection of some T. 'count' is the number of items in the collection. I n...
Using Generics in Interfaces
How do I allow my CookieData to be generic in the following code? I get an compile-time error on the declaration of ICookieService2. public struct CookieData<T> { T Value { get; set; } DateTime Expires { get; set; } } public interface ICookieService2: IDictionary<string, CookieData<T>> { // ... } My error is: The type...
Where are generic types stored in java class files?
I am well aware that generic types are erased from Java code when it is compiled. What information (attributes?) do 1.5+ JVMs use to implement getGenericType , etc. ? ...
Java Generics and reflection!
I have a class that looks like this: public class UploadBean { protected UploadBean(Map<String,?> map){ //do nothing. } } To use reflection and create a object by invoking the corresponding constructor, I wrote code as follows: Class<?> parTypes[] = new Class<?>[1]; parTypes[0] = Map.class; Constructor ct = format.g...
IList implementations fall into three categories: read-only, fixed-size, variable-size
What does this mean? I am returning a IList<T> from my business layer and then adding items from the UI, but the app is complaining that it's a fixed-size list. How can I overcome this problem? ...
.NET Generic Parameters for Generic Lists
Running .NET 2.0, I have a generic method with the following signature: static listType FillCollection<listType, objType>(IDataReader dr) where listType : ICollection<objType>, new() it's purposes is to translate a datareader into a collection of objects both of my choosing. My problem, which isn't exactly a problem, is that when I c...
How to reduce type declarations when using lambda parameters?
Below is a heavily cut down version of some code I have public class DataInfo<T> { public DataInfo(string description, Func<T, object> funcToGetValue) { this.description = description; this.funcToGetValue= funcToGetValue; } public readonly string description; public readonly Func<T, object> funcToGet...
C# How do you use foreach on a base class using generics?
This question is as a result of trying Jon Skeet's answer to this question. So I have the following code based in the question and answer from the above question link. public abstract class DeliveryStrategy { } public class ParcelDelivery : DeliveryStrategy { } public class ShippingContainer : DeliveryStrategy { } public abstract cla...
How can I add a type constraint to include anything serializable in a generic method?
My generic method needs to serialize the object passed to it, however just insisting that it implements ISerializable doesn't seem to work. For example, I have a struct returned from a web service (marked with SerializableAttribute) that serializes to xml just fine, but, as expected, the C# compiler complains. Is there a way I can check...