using System;

public class Program

{

    public static void Main()

    {

        var c = new C();

        var result = c.GetAnotherObject(new BImpl<string, int>());

        Console.WriteLine(result);

    }

}

​

public class BImpl<T, V> : A<T, V>.B

{

    public override int BM()

    {

        return 1;

    }

}

​

// Or you can supply type arguments right here

//public class BImpl : A<string, int>.B

//{

//  public override int BM()

//  {

//      return 1;

//  }

//}

​

public abstract class A<T, V>

{

    public abstract int GetObject(T t, V v);

    public abstract int GetAnotherObject(B b);

    public abstract class B

    {

        public abstract int BM();

    }

}

​

public class C : A<string, int>

{

    public C()

    {

​

    }

​

    public override int GetObject(string abc, int def)

    {

        return 10;

    }

​

    public override int GetAnotherObject(B b)

    {

        return b.BM();

    }

}