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21.2 使用数据库连接
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21.2 使用数据库连接
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<link href="css.css" rel="stylesheet" type="text/css" /><h3 style="MARGIN-TOP: 11.4pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 11.4pt"><a ftel="_Toc507815158"><span lang="EN-GB">21.2 </span></a><span style="FONT-FAMILY: 楷体_GB2312">使用数据库连接</span></h3>
<p class="MsoNormal" style="LINE-HEIGHT: 16pt"><a ftel="connections"><span style="FONT-FAMILY: 宋体">为了访问数据库</span></a><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">需要提供某种类型的连接参数</span><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">例如运行数据库的机器</span><span style="FONT-FAMILY: 宋体">，和</span><span style="FONT-FAMILY: 宋体">登录凭证。使用</span><span lang="EN-US">ADO</span><span style="FONT-FAMILY: 宋体">的用户会很快熟悉</span><span lang="EN-US">.NET</span><span style="FONT-FAMILY: 宋体">连接类</span><span lang="EN-US">OleDbConnection</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">SqlConnection</span><span style="FONT-FAMILY: 宋体">，图</span><span lang="EN-US">21-1</span><span style="FONT-FAMILY: 宋体">显示了连接类及它们支持的接口。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在本章的示例中，使用</span><span lang="EN-US">Northwind</span><span style="FONT-FAMILY: 宋体">数据库，它是和</span><span lang="EN-US">.NET Framework SDK</span><span style="FONT-FAMILY: 宋体">示例一起安装的。下面的代码段说明了如何创建、打开和关闭</span><span lang="EN-US">Northwind</span><span style="FONT-FAMILY: 宋体">数据库的连接。</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-GB">using System.Data.SqlClient;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB"> </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB">string source = "server=(local)\\NetSDK;" +</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB"> "integrated security=SSPI;" + </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB"> "database=Northwind";</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB">SqlConnection conn = new SqlConnection(source);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB">conn.Open();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB"> </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB">// Do something useful</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-GB"> </span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-GB">conn.Close();</span></p>
<p align="center"><span lang="EN-US"><img height="167" src="21/image001.jpg" width="437" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 21-1</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">如果以前使用过</span><span lang="EN-US">ADO</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">OLE DB</span><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">就会很熟悉连接字符串。如果使用的是</span><span lang="EN-US">OleDb</span><span style="FONT-FAMILY: 宋体">提供程序</span><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">就应能剪切和粘贴旧代码。在该示例的连接字符串中，使用的参数如下所示。连接字符串中的参数用分号分隔开。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-US">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">server=(local)\\NetSDK</span><span style="FONT-FAMILY: 宋体">：表示要连接的数据库服务器。</span><span lang="EN-US">SQL Server</span><span style="FONT-FAMILY: 宋体">允许在同一台机器上运行多个不同的数据库服务器进程，所以这里在本地机器上连接</span><span lang="EN-US">NetSDK</span><span style="FONT-FAMILY: 宋体">进程。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-US">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-GB">integrated security=SSPI</span><span style="FONT-FAMILY: 宋体">：这个参数使用</span><span lang="EN-US">Windows Authentication</span><span style="FONT-FAMILY: 宋体">连接数据库，最好在源代码中使用这个参数，而不是用户名和密码。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-US">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">database=Northwind</span><span style="FONT-FAMILY: 宋体">：这描述了要连接的数据库实例。每个</span><span lang="EN-US">SQL Server</span><span style="FONT-FAMILY: 宋体">进程都可以有几个数据库实例。</span></p>
<p class="MsoBodyTextIndent"><span style="FONT-FAMILY: 宋体">这个示例使用定义的连接字符串打开数据库连接，再关闭该连接。连接打开后，就可以对数据源执行命令，完成后，就可以关闭连接。</span></p>
<p class="MsoNormal"><span lang="EN-US">SQL Server</span><span style="FONT-FAMILY: 宋体">有另一个模式的身份验证。它可以使用</span><span lang="EN-US">Windows</span><span style="FONT-FAMILY: 宋体">集成的安全性，这样在登录时提供的证书就会传送给</span><span lang="EN-US">SQL Server</span><span style="FONT-FAMILY: 宋体">。这适合于删除连接字符串的</span><span lang="EN-US">uid </span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US"> pwd</span><span style="FONT-FAMILY: 宋体">部分，并添加</span><span lang="EN-US">Integrated Security=SSPI</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在本章的下载代码中，有一个文件</span><span lang="EN-US">Login.cs</span><span style="FONT-FAMILY: 宋体">简化了本章的示例。它链接了所有的示例代码，包括用于这些示例的数据库连接信息；可以修改该文件，使用自己的服务器名称、用户和密码。在默认情况下，该文件使用</span><span lang="EN-US">Windows</span><span style="FONT-FAMILY: 宋体">集成的安全性，但是可以根据需要修改用户名和密码。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">下一小节介绍使用</span><span lang="EN-US">ADO.NET</span><span style="FONT-FAMILY: 宋体">的一些好方法。</span></p></div>
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