演示C#三层的开发框架,是一个经典的例子,可以好好学习,安装之后,会建立一个目录,解压出所有的源代码(环境是VS 2005 C#)+SQL 2005 express edition-Demo three-tier C# development framework, is a classic example, you can study well and installed, will create a directory, unzip all the source code (the envir