using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(new Test("Ivan").SayHello());

    }

}

​

public interface ITest

{

    string text { get; set; }

}

​

public static class ITestExtensions

{

    public static string SayHello(this ITest test)

    {

        return test.text + " HELLO CHUJU";  

    }

}

​

public class Test: ITest

{

    public string text { get; set; }

    public Test (string text)

    {

        this.text = text;

    }

}

​

​

​

​