using System;

using System.Collections;

using System.Collections.Generic;

public interface MyInterfaceFunc {

    void Call<T>(MyInterface<T> obj);

}

​

public interface MyInterface {

    void Generically(MyInterfaceFunc func);  // this is the key!

}

​

public interface MyInterface<T> : MyInterface

{

    T GetSomething();

    void DoSomething(T something);

}

​

public class MyIntClass : MyInterface<int>

{

    public int GetSomething()

    {

        return 42;

    }

​

    public void DoSomething(int something)

    {

        Console.Write(something);

    }

​

    public void Generically(MyInterfaceFunc func) {

        func.Call(this);

    }

}

​

public class MyStringClass : MyInterface<string>

{

    public string GetSomething()

    {

        return "Something";

    }

​

    public void DoSomething(string something)

    {

        Console.Write(something);

    }

​

    public void Generically(MyInterfaceFunc func) {

        func.Call(this);

    }

}

public class MyFunc : MyInterfaceFunc {

    public void Call<T>(MyInterface<T> thingDoer) {

        T something = thingDoer.GetSomething();

        thingDoer.DoSomething(something);

        thingDoer.DoSomething(something);

    }

}

​

public class Program {

    public static void Main(){

        var listOfThings = new List<MyInterface>(){

            new MyIntClass(),

            new MyStringClass()

        };

​

        foreach (MyInterface thingDoer in listOfThings){

            thingDoer.Generically(new MyFunc());

        }

    }

}