Python高级编程 C#高级编程：选择数据[1]

C#高级编程：选择数据[1]  

    定义了数据连接后 就可以从可用的列表中选择一个表(或视图) 把该表从项目中拖放到活动的窗体上 如图 所示

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    在本例中 选择Customers表 把这个对象拖放到项目中时(可以把它拖放到窗体上 或者拖放到服务器控件面板上) 就会在窗体上添加一个派生于SqlDataAdapter或 OleDbDataAdaptor的对象(如果没有使用SQL Server)

    生成的数据适配器包含SELECT INSERT UPDATE和DELETE命令 显然 也可以调用存储过程 而不直接使用SQL命令 向导生成的代码也可以完成这个工作 Visual Studio NET给 cs文件添加如下代码     private System Data SqlClient SqlCommand sqlSelectCommand ;     private System Data SqlClient SqlCommand sqlInsertCommand ;     private System Data SqlClient SqlCommand sqlUpdateCommand ;     private System Data SqlClient SqlCommand sqlDeleteCommand ;     private System Data SqlClient SqlDataAdapter sqlDataAdapter ;

    为每个SQL命令定义一个对象和一个SqlDataAdapter 在文件后面的InitializeComponent方法中 向导生成了创建这些命令和数据适配器的代码

    在Visual Studio NET生成的代码中 需要解释两个地方 UpdateCommand和InsertCommand属性 下面是显示有关信息的节选版本     //     // sqlInsertCommand     //     this sqlInsertCommand CommandText = @ INSERT INTO Customers                                     (CustomerID CompanyName ContactName                                     ContactTitle Address City Region                                     PostalCode Country Phone Fax)           VALUES(@CustomerID @CompanyName @ContactName @ContactTitle                  @Address @City @Region @PostalCode @Country @Phone @Fax);           SELECT CustomerID CompanyName ContactName ContactTitle Address                  City Region PostalCode Country Phone Fax           FROM Customers WHERE (CustomerID = @CustomerID) ;     this sqlInsertCommand Connection = this sqlConnection ;           this sqlInsertCommand Paramaters Add(           new System Data SqlClient SqlParamater( @CustomerID               System Data SqlDbType NVarChar CustomerID ));           // Other Paramaters omitted for clarity           //     // sqlUpdateCommand     //           this sqlUpdateCommand CommandText = @ UPDATE Customers                   SET CustomerID = @CustomerID CompanyName = @CompanyName                       ContactName = @ContactName ContactTitle = @ContactTitle                       Address = @Address City = @City Region = @Region                       PostalCode = @PostalCode Country = @Country