C#高级编程：选择数据[1]

——此文章摘自《C#高级编程（第版）》定价元 特价元 购买

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

图

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SELECTINSERTUPDATE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 SystemDataSqlClientSqlCommand sqlSelectCommand;

private SystemDataSqlClientSqlCommand sqlInsertCommand;

private SystemDataSqlClientSqlCommand sqlUpdateCommand;

private SystemDataSqlClientSqlCommand sqlDeleteCommand;

private SystemDataSqlClientSqlDataAdapter 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

//

thissqlInsertCommandCommandText = @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);

thissqlInsertCommandConnection = thissqlConnection;

thissqlInsertCommandParamatersAdd(

new SystemDataSqlClientSqlParamater(@CustomerID

SystemDataSqlDbTypeNVarChar CustomerID));

// Other Paramaters omitted for clarity

//

// sqlUpdateCommand

//

thissqlUpdateCommandCommandText = @UPDATE Customers

SET CustomerID = @CustomerID CompanyName = @CompanyName

ContactName = @ContactName ContactTitle = @ContactTitle

Address = @Address City = @City Region = @Region

PostalCode = @PostalCode Country = @Country

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