using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var list = new ABList<dynamic>();

    }

}

​

public interface X { void Foo(); }

​

public interface Y { void Bar(); }

​

public class A : X, Y

{

    public void Foo() {}

    public void Bar() {}

}

​

public class B : X, Y

{

    public void Foo() {}

    public void Bar() {}

}

​

public class ABList<T> : List<T> where T : X, Y

{

    // implement me

}