using System;

using System.Globalization;

using System.Diagnostics;

using System.Linq;

using System.Linq.Expressions;

using System.Collections;

using System.Collections.Generic;

using System.Threading;

using System.Threading.Tasks;

using System.Xml;

using System.Xml.XPath;

using System.Xml.Linq;

using System.Drawing;

​

public class Program

{

    public static void Main()

    {

        var dev = new Developer();

        dev.Register("senior"); 

        IEmployee e = dev;

        e.Register("senior");   

    }

}

​

public interface IEmployee

{

    void Register(string role);

}

​

public abstract class Employee : IEmployee

{

    public void Register(string role)

    {

        Console.WriteLine(role);

    }

}

​

// Case 2

public class Developer : Employee, IEmployee

{

    public void Register(string role)

    {

        Console.WriteLine("i'm developer!");

    }

}

​

/*

// Case 2

public class Developer : Employee

{

    public void Register(string role)

    {

        Console.WriteLine("i'm developer!");

    }

}

*/

​