用多层架构构建一个简易留言本

;           // …..



            dt.Columns["Id"].AutoIncrement = true;

            dt.Columns["Id"].AutoIncrementSeed = 0;

            dt.Columns["Id"].AutoIncrementStep = -1;

            dt.PrimaryKey = new DataColumn {dt.Columns["Id"]};



            this.Tables.Add(dt);

        }

    AddedNewRow属性返回一个新增进数据表的、空的DataRow，用于给逻辑层填充。FillDataFormDataBase()的两个重载调用数据访问层的相应方法来填充一个新的CMessageData对象并返回。UpdateToDatabase用于讲自身的数据更改更新回数据库。

public DataRow AddedNewRow()…

public static CMessageData FillDataFromDatabase(Int32 startRecord, Int32 maxRecord)…

public static CMessageData FillDataFromDatabase(Int32 id)…

public void UpdateToDatabase()…

         

二、数据访问层(CDataAccess类)

负责连接数据库，进行SIUD(Select,Insert,Update,Delete)操作。数据连接信息放在AppParameters.xml文件中。



FillMessageData()的两个重载创建新的CMessageData对象，填充数据，然后返回：

public static CMessageData FillMessageData(Int32 startRecord, Int32 maxRecord)

public static CMessageData FillMessageData(Int32 id)



UpdateMessageData()把参数中的CMessageData对象所作出的更改更新回数据库：

public static Int32 UpdateMessageData(CMessageData messageData) {

            OleDbConnection conn = new OleDbConnection(CAppParameters.OleDbConnectionString);

            OleDbCommand cmdSelect = new OleDbCommand("Select username,last_reply_time,guest_name,guest_email,guest_website_name,guest_website_url,guest_oicq,guest_ip,guest_post_time,guest_text,reply_data From t_gbook_postinfo", conn);



            OleDbCommand cmdInsert = new OleDbCommand();

            cmdInsert.Connection = conn;

            cmdInsert.CommandText = "Insert Into t_gbook_postinfo (last_reply_time,guest_name,guest_email,guest_website_name,guest_website_url,guest_oicq,guest_ip,guest_post_time,guest_text,reply_data) Values (@last_reply_time,@guest_name,@guest_email,@guest_website_name,@guest_website_url,@guest_oicq,@guest_ip,@guest_post_time,@guest_text,@reply_data)";

            cmdInsert.Parameters.Add("@last_reply_time", OleDbType.DBDate, 0, "last_reply_time");