Calculate the length of an empty string, we'll get zero; but for a null string, we'll encounter a NullReferenceException.
using System; public class MainClass { public static void Main(String[] argv) {//from ww w .jav a 2 s. c o m string emptyString = String.Empty; string nullString = null; Console.WriteLine("Length of emptyString is {0}", emptyString.Length);//0 //Console.WriteLine("Length of nullString is {0}", nullString.Length); //Exception Console.WriteLine(emptyString == "");//True Console.WriteLine(nullString == "");//False Console.WriteLine(string.IsNullOrEmpty(emptyString));//True Console.WriteLine(string.IsNullOrEmpty(nullString));//True } }