using System;

public class Program

{

    public static void Main()

    {

        string nullString = null;

        Console.WriteLine("nullString is null? {0}",nullString == null);

​

        string emptyString = nullString.EmptyIfNull();

        Console.WriteLine("emptyString is null? {0}",emptyString == null);

        string anotherNullString = emptyString.NullIfEmpty();

        Console.WriteLine("anotherNullString is null? {0}",anotherNullString == null);

    }

}

​

static class StringExtensions

{

        public static string EmptyIfNull(this string text)

        {

            return text ?? String.Empty;

        }

        public static string NullIfEmpty(this string text)

        {

            return string.Empty == text ? null : text;

        }

}