using System;

​

​

interface B 

{

}

​

interface C 

{

}

​

class D : B,C

{

}

​

public class Person

{

    public string FirstName { get; set; }

    public string LastName  { get; set; }

    public override string ToString()

    {

        return string.Format("{0}: {1} {2}", GetType(), FirstName, LastName);

    }

    public override int GetHashCode()

    {

        return FirstName.GetHashCode() ^ LastName.GetHashCode();

    }

}

​

public class Program

{

    public static void Main()

    {

        var person = new Person() { FirstName = "John", LastName = "Doe" };

        log(person);

        log(person.GetHashCode());

    }

    public static void log(object o) { Console.WriteLine(o == null ? "null" : o.ToString()); }

}