using System;

using System.Collections.Generic;

using System.Linq;

​

public interface ISomeInterface{}

public class SomeInterfaceImplA : ISomeInterface{}

public class SomeInterfaceImplB : ISomeInterface{}

public class SomeClass

{

    private IList<Action<ISomeInterface>> _delegates = new List<Action<ISomeInterface>>();

    public IEnumerable<Action<ISomeInterface>> Delegates{ get {return _delegates;} }

    public void AddDelegate<T>(Action<T> del) where T : ISomeInterface

    {

        _delegates.Add(si => del((T)si));   

    }

}

public class Program

{

    public static void Main()

    {

        var someClass = new SomeClass();

        Action<SomeInterfaceImplA> someInterfaceImplADelegate = delegate(SomeInterfaceImplA siia){Console.WriteLine("SomeInterfaceImplADelegate");}; 

        Action<SomeInterfaceImplB> someInterfaceImplBDelegate = delegate(SomeInterfaceImplB siib){Console.WriteLine("SomeInterfaceImplBDelegate");}; 

        someClass.AddDelegate(someInterfaceImplADelegate);

        someClass.AddDelegate(someInterfaceImplBDelegate);

        var aDelegates = someClass.Delegates.Where(d => d is Action<SomeInterfaceImplA>);//What predicate should be used....

        foreach(var del in aDelegates)

        {

            del(null); //...in order to only iterate over delegates with type SomeInterfaceImplA?

        }

    }

}