怎样用VS2005进行三层结构应用程序的开发.doc

?用VS2005.NET进行三层结构应用程序的开发 １.三层之间的关系：三层是指：界面显示层(UI)，业务逻辑层(Business)，数据操作层(Data Access)文字描述：Clients对UI进行操作，UI调用Business进行相应的运算和处理，Business通过Data Access对Data Base进行操作。 ?优点： 1、增加了代码的重用。Data Access可在多个项目中公用；Business可在同一项目的不同地方使用（如某个软件B/S和C/S部分可以共用一系列的Business组件）。 2、使得软件的分层更加明晰，便于开发和维护。美工人员可以很方便地设计UI设计，并在其中调用Business给出的接口，而程序开发人员则可以专注的进行代码的编写和功能的实现。 ２.Data Access的具体实现： DataAgent类型中变量和方法的说明： ? private string m_strConnectionString; //连接字符串 private OleDbConnection m_objConnection; //数据库连接 ? public DataAgent(string strConnection) //构造方法，传入的参数为连接字符串 private void OpenDataBase() //打开数据库连接 private void #region CloseDataBase() //关闭数据库连接 public DataView GetDataView(string strSqlStat) //根据传入的连接字符串返回DataView ? 具体实现代码如下： ?public class DataAgent ?????? { ?????????? #region Variables ?????????private string m_strConnectionString; ?????????private OleDbConnection m_objConnection; ?????????? #endregion Variables ?????????? #region Functions ?????????? #region DataAgend ?????????///summary ?????????/// Initial Function ?????????////summary ?????????///param name=strConnection/param ?????????public DataAgent(string strConnection) ?????????? { ??????????????this.m_strConnectionString = strConnection; ?????????? } ?????????? #endregion DataAgend ?????????? #region OpenDataBase ?????????///summary ?????????/// function to open data base ?????????////summary ?????????private void OpenDataBase() ?????????? { ??????????????try ??????????????? { ???????????????????this.m_objConnection = new OleDbConnection(); ???????????????????this.m_objConnection.ConnectionString = this.m_strConnectionString; ???????????????????if(this.m_objConnection.State != ConnectionState.Open) ???????????????????? { ???????????????????????this.m_objConnection.Open(); ???????????????????? } ??????????????? } ??????????????catch(Exception e) ??????????????? { ???????????????????throw e; ??????????????? } ?????????? } ?????????? #endregion OpenDataBase ?????????? #region CloseDataBase ?????????///summary ?????????/// t