Class extension example

 namespace ConsoleApplication1  
 {  
   public static class MyExtensions  
   {  
     public static int WordCount(this String str)  
     {  
       return str.Split(new char[] { ' ', '.', '?' },  
         StringSplitOptions.RemoveEmptyEntries).Length;  
     }  
   }  
   class Program  
   {  
     static void Main(string[] args)  
     {  
       string s = "1.2.3";  
       Console.WriteLine( s.WordCount().ToString());  
       Console.ReadKey();  
     }  
   }  
 }