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22.3.2 选择数据
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C#高级编程（第3版）
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22.3.2 选择数据
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<div style='float:left;width:49%'>·<a href='100165626.htm'>22.2.2 数据绑定对象</a></div><div style='float:right;width:49%'>·<a href='100165627.htm'>22.3 Visual Studio .NET和数据访问</a></div><div style='float:left;width:49%'>·<a href='100165628.htm'>22.3.1 创建一个连接</a></div><div style='float:right;width:49%'>·<a href='100165630.htm'>22.3.3 生成DataSet</a></div><div style='float:left;width:49%'>·<a href='100165631.htm'>22.3.4 更新数据源</a></div><div style='float:right;width:49%'>·<a href='100165632.htm'>22.3.5 构建模式</a></div></div>
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<link href="css.css" rel="stylesheet" type="text/css" /><h3 style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 8.15pt"><a ftel="_Toc507815188"><span lang="EN-US">22.3.2 </span></a><span style="FONT-FAMILY: 黑体">选择数据</span></h3>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">定义了数据连接后，就可以从可用的列表中选择一个表</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">或视图</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，把该表从项目中拖放到活动的窗体上，如图</span><span lang="EN-US">22-21</span><span style="FONT-FAMILY: 宋体">所示。</span></p>
<p align="center"><span lang="EN-US"><img height="174" src="22/image021.jpg" width="178" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 22-21</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在本例中，选择</span><span lang="EN-US">Customers</span><span style="FONT-FAMILY: 宋体">表。把这个对象拖放到项目中时</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">可以把它拖放到窗体上，或者拖放到服务器控件面板上</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，就会在窗体上添加一个派生于</span><span lang="EN-US">SqlDataAdapter</span><span style="FONT-FAMILY: 宋体">或</span> <span lang="EN-US">OleDbDataAdaptor</span><span style="FONT-FAMILY: 宋体">的对象</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">如果没有使用</span><span lang="EN-US">SQL Server)</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">生成的数据适配器包含</span><span lang="EN-US">SELECT</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">INSERT</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">UPDATE</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">DELETE</span><span style="FONT-FAMILY: 宋体">命令。显然，也可以调用存储过程，而不直接使用</span><span lang="EN-US">SQL</span><span style="FONT-FAMILY: 宋体">命令。向导生成的代码也可以完成这个工作。</span><span lang="EN-US">Visual Studio .NET</span><span style="FONT-FAMILY: 宋体">给</span><span lang="EN-US">.cs</span><span style="FONT-FAMILY: 宋体">文件添加如下代码：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">private System.Data.SqlClient.SqlCommand sqlSelectCommand1;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">private System.Data.SqlClient.SqlCommand sqlInsertCommand1;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">private System.Data.SqlClient.SqlCommand sqlUpdateCommand1;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">private System.Data.SqlClient.SqlCommand sqlDeleteCommand1;</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">private System.Data.SqlClient.SqlDataAdapter sqlDataAdapter1;</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">为每个</span><span lang="EN-US">SQL</span><span style="FONT-FAMILY: 宋体">命令定义一个对象和一个</span><span lang="EN-US">SqlDataAdapter</span><span style="FONT-FAMILY: 宋体">。在文件后面的</span><span lang="EN-US">InitializeComponent</span><span style="FONT-FAMILY: 宋体">方法中，向导生成了创建这些命令和数据适配器的代码。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在</span><span lang="EN-US">Visual Studio .NET</span><span style="FONT-FAMILY: 宋体">生成的代码中，需要解释两个地方：</span><span lang="EN-US">UpdateCommand</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">InsertCommand</span><span style="FONT-FAMILY: 宋体">属性。下面是显示有关信息的节选版本：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">// </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">// sqlInsertCommand1</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">// </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">this.sqlInsertCommand1.CommandText = @"INSERT INTO Customers </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> (CustomerID, CompanyName, ContactName, </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> ContactTitle, Address, City, Region, </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> PostalCode, Country, Phone, Fax)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> VALUES(@CustomerID, @CompanyName, @ContactName, @ContactTitle, </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> @Address, @City, @Region, @PostalCode, @Country, @Phone, @Fax);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> SELECT CustomerID, CompanyName, ContactName, ContactTitle, Address, </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> City, Region, PostalCode, Country, Phone, Fax </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> FROM Customers WHERE (CustomerID = @CustomerID)";</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">this.sqlInsertCommand2.Connection = this.sqlConnection1;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> </span></p>
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