Convert Class Where T : IMySampleInterface to Class

Question

Is it possible to convert Class<T> Where T : IMySampleInterface to Class<IMySampleInterface>

Example:

public abstract class AbstractCommunication: ICommunication
{
    private ICommunicationCallback<ICommunication> callback = null;
    public void registerCommunicationCallback<T>(ICommunicationCallback<T> callback) where T : ICommunication
    {
        this.callback =  (ICommunicationCallback<ICommunication>)callback; //<--DOESNT WORK
    }
}

In my Example the following exception occurs: System.InvalidCastException

Edit:

public interface ICommunicationCallback<T> where T : ICommunication
{
    void onCommunicationCallback(T sender, String data);
}

why do i use this way: If I have a base class that should implement for example two Callbacks than i could simply use the following:

public class TestClass : ICommunicationCallback<TestClass1>, ICommunicationCallback<TestClass2>

TestClass1:

public class TestClass1: AbstractCommunication
{

}

TestClass2:

public class TestClass2: AbstractCommunication
{

}

Edit: "if T is always an ICommunication, then why keep it generic? – Davin Tryon 20 mins ago" Im locking at this point

Okay Without the generics i got the same error but different System.InvalidCastException: (That is why i used generics in the first place - i remember now)

 public class DocumentTest : ICommunicationCallback<GetDocumentData>
    {
     public void callAsync()
{
     CommunicationFactory comFactory = new CommunicationFactory(communicationServiceClient);
                GetDocumentData getDocumentData = (GetDocumentData)comFactory.createCommunicationObject(CommunicationFactory.ENTITY_TYPE.GET_DOCUMENT_DATA,(ICommunicationCallback<ICommunication> ) this);

}

}

public interface ICommunicationCallback<ICommunication> 
{
    void onCommunicationCallback(ICommunication sender, String data);
}

I Think using generics is the only solution in my case - see: "This feature works only for generic interfaces and delegates. If you implement a variant generic interface, the implementing class is still invariant. Classes and structs do not support variance in C# 4.0. So the following doesn’t compile: // List implements the covariant interface // IEnumerable. But classes are invariant. List list = new List(); // Compiler error here." (http://blogs.msdn.com/b/csharpfaq/archive/2010/02/16/covariance-and-contravariance-faq.aspx)

you need to define `` at the class level, not at the method level. — Ryan Gates, Mar 08 '13 at 14:58
if `T` is always an `ICommunication`, then why keep it generic? — Davin Tryon, Mar 08 '13 at 15:00
Did you look at the following questions? [“Base abstract generic class is a bad choice in most situations.” Why? (Or Why not)](http://stackoverflow.com/q/5040814/299327) and [Using generics in abstract classes](http://stackoverflow.com/q/2359540/299327) — Ryan Gates, Mar 08 '13 at 15:02

Frank59 · Answer 1 · 2013-03-08T15:53:16.730

interface ICommunication
{
}

interface ICommunicationCallback<T>
{
}

class AbstractCommunicationCallback<T> : ICommunicationCallback<T>
{

}

abstract  class AbstractCommunication : ICommunication
{
    private ICommunicationCallback<ICommunication> callback = null;
    public void registerCommunicationCallback<T>(ICommunicationCallback<T> callback) where T : ICommunication
    {
        this.callback = (ICommunicationCallback<ICommunication>)callback; //<--DOESNT WORK
    }
}

class Communication : AbstractCommunication { 
}

and test method

public void Test()
    {
          AbstractCommunication comm = new Communication();
         AbstractCommunicationCallback<ICommunication> callback = new AbstractCommunicationCallback<ICommunication>();
        comm.registerCommunicationCallback(callback);
    }

working without error on .net framework 4, vs 2010

EDIT: some interesting info http://msdn.microsoft.com/en-us/library/ee207183.aspx

frugi · Accepted Answer · 2013-03-11T15:06:33.790

0

I solved my Problem. But I haven't used generics - I use the ICommunication Interface.

public interface ICommunicationCallback
{
    void onCommunicationCallback(ICommunication sender, CommunicationResultObject result);
}

This solution in my opinion isn't that elegant but it works.

edited Mar 11 '13 at 15:06

answered Mar 11 '13 at 09:33

frugi

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Convert Class Where T : IMySampleInterface to Class

2 Answers2