[RESOLVED] Understanding Interfaces

[motil]

I'm trying to fully understand the interface concept so bare with me

let's say i created this interface:

public interface INameable
    {
         string FirstName { set; get; }
         string LastName { set; get; }
         string GetLastNameFirst();
    }

and implement its properties and methods in this class:

 public class entity : INameable
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string GetLastNameFirst()
        {
            return String.Format("{0} {1}", FirstName, LastName);
        }
    }

now i want to implement this interface in another class but i don't want to
re-write "GetLastNameFirst" method since i already wrote it in the above class
(entity)

so how do i re-use that method in my new class:

 public class Worker : INameable
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }

       // here i don't want to re-write the method, i just want to re-use the
       // method i wrote in the above entity class)
        public string GetLastNameFirst()
        {
            return "???";
        }

    }

any pointers or direction will be appreciated!