设计模式之Singleton(单态)
http://www.jdon.com/designpatterns/singleton.htm

Singleton设计模式的C#实现(1)

http://www.aspcool.com/lanmu/browse1.asp?ID=1138&bbsuser=csharp

C#实现Singleton (转载)

http://www.cnblogs.com/supercode/archive/2005/06/13/173526.html