using System;

​

public interface IA

{

    void Method1();

    void Method2();

}

​

public class ClassB

{

    public void Method2()

    {

        Console.WriteLine("Method2");

    }

}

​

public class ClassC : ClassB, IA

{

    public void Method1()

    {

        Console.WriteLine("Method1");

    }

}

​

public class Program

{

    public static void Main()

    {

        var c = new ClassC();

        c.Method1();

        c.Method2();

    }

}