...One approach is to use an idiom referred to as Double-Check Locking [Lea99]. However, C# in combination with the common language runtime provides a static initialization approach, which circumvents these issues without requiring the developer to explicitly code for thread safety.

Singleton.cs

// from http://msdn.microsoft.com/en-us/library/ff650316.aspx

public sealed class Singleton
{
   private static readonly Singleton instance = new Singleton();
   
   private Singleton(){}

   public static Singleton Instance
   {
      get 
      {
         return instance; 
      }
   }
}