using System;

using System.Linq;

using System.Collections.Generic;

public interface ITest<in TIn, out TOut> 

    where TIn : class, new()

    where TOut: class, new()

{

    //TOut MyFunction(Func<TIn, Tout> transform);

    TOut MyFunction(Func<TOut, TIn> transform);

    TOut GetSomething();

    void WriteSomething(TIn arg);

}

​

class Base

{

    public string BaseMiddleAndDerived { get; set; }

}

​

class Middle : Base

{

    public string BaseAndMiddleOnly { get; set; }

}

class Derived : Middle

{

    public string DerivedOnly { get; set; }

}

​

​

class Test<TIn, TOut> : ITest<TIn, TOut> 

    where TIn : Base, new()

    where TOut: Base, new()

{

    public TOut MyFunction(Func<TOut, TIn> transform)

    {

        return new TOut();

    }

    public TOut GetSomething()

    {

        return new TOut();

    }

    public void WriteSomething(TIn arg)

    {

        Console.WriteLine(arg.BaseMiddleAndDerived);

    }

}

​

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}