说明：  一个C#关于数据库（SQL例）的关于数据交互、数据基本操作的很完整的类文件，几乎涵盖了所有的数据操作，编程结构很清晰
(A C# on the database (SQL cases) on the data exchange, data, the basic operation of the class file very complete, covering almost all of the data manipulation, programming structure is very clear)