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21.1.3 数据库特定的类
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C#高级编程（第3版）
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21.1.3 数据库特定的类
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<div style='float:left;width:49%'>·<a href='100165592.htm'>21.1 ADO.NET概述</a></div><div style='float:right;width:49%'>·<a href='100165593.htm'>21.1.1 命名空间</a></div><div style='float:left;width:49%'>·<a href='100165594.htm'>21.1.2 共享类</a></div><div style='float:right;width:49%'>·<a href='100165596.htm'>21.2 使用数据库连接</a></div><div style='float:left;width:49%'>·<a href='100165597.htm'>21.2.1 高效地使用连接</a></div><div style='float:right;width:49%'>·<a href='100165598.htm'>21.2.2 事务处理</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="_Toc507815156"><span lang="EN-US">21.1.3 </span></a><span style="FONT-FAMILY: 黑体">数据库特定的类</span></h3>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">除了共享类外，</span><span lang="EN-US">ADO.NET</span><span style="FONT-FAMILY: 宋体">还包含许多数据库特定的类，如下所示。这些类执行一组在</span><span lang="EN-US">System.Data</span><span style="FONT-FAMILY: 宋体">命名空间中定义的标准接口，允许类按照以一般形式来使用。例如</span><span style="FONT-FAMILY: 宋体">，</span><span lang="EN-US">SqlConnection</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">OleDbConnection</span><span style="FONT-FAMILY: 宋体">类执行</span><span lang="EN-US">IDbConnection</span><span style="FONT-FAMILY: 宋体">接口。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-GB">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">SqlCommand</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OleDbCommand</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OracleCommand</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ODBCCommand</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span lang="EN-GB">SQL</span><span style="FONT-FAMILY: 宋体">语句的包装器或存储过程的调用。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-GB">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">SqlCommandBuilder</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OleDbCommandBuilder</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OracleCommandBuilder</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ODBCCommand Builder</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">用于从一个</span><span lang="EN-GB">select</span><span style="FONT-FAMILY: 宋体">子句中生成</span><span lang="EN-GB">SQL</span><span style="FONT-FAMILY: 宋体">语句</span><span lang="EN-GB">(</span><span style="FONT-FAMILY: 宋体">例如</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">语句</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">的类。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-GB">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">SqlConnection</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OleDbConnection</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OracleConnection</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ODBCConnection</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">数据库连接。类似于</span><span lang="EN-GB">ADO </span><span lang="EN-US">Connection</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="1" style="MARGIN-LEFT: 31.55pt; FTEL: -10.1pt"><span lang="EN-GB">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-GB" style="FONT-FAMILY: 宋体; LETTER-SPACING: -2pt"> </span><span lang="EN-US">SqlDataAdapter</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OleDbDataAdapter</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OracleDataAdapter</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ODBCDataAdapter</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">用于存储选择、插入、更新和删除语句的类，因此可以用于生成</span><span lang="EN-US">DataSet</span><span style="FONT-FAMILY: 宋体">和更新数据库。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-GB">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">SqlDataReader</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OleDbDataReader</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OracleDataReader</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ODBCDataReader</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">只向前的连接数据读取器。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-GB">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">SqlParameter</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OleDbParameter</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OracleParameter</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ODBCParameter</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">为存储过程定义一个参数。</span></p>
<p class="1" style="MARGIN-LEFT: 37.55pt; FTEL: -16.1pt"><span lang="EN-GB">●<span style="FONT: 7pt 'Times New Roman'"> </span></span><span lang="EN-US">SqlTransaction</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OleDbTransaction</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">OracleTransaction</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">ODBCTransaction</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="FONT-FAMILY: 宋体">数据库事务处理，包装在一个对象中。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 16pt"><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">从上面的列表可以看出，每种对象都有</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">4</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">个类，分别用于</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">.NET 1.1</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">中的每个提供程序。在本章的后面部分，除非特别说明，否则前缀</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt"><provider></span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">将用于表示所使用的类依赖于数据库提供程序。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 16pt"><span lang="EN-US" style="LETTER-SPACING: 0.1pt">ADO.NET</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">类最重要的新特性是它们是以断开连接的方式工作</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">，</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">这在目前以</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">Web</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">为中心的环境中是非常重要的。我们常常把服务</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">(</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">例如在线书店</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">)</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">构建为连接一个服务器，检索一些数据，再在客户</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">PC</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">上处理这些数据，之后重新连接服务器，把数据传送回去，进行处理。</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">ADO.NET</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">的断开连接的本质就可以实现这种操作。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 16pt"><span lang="EN-US" style="LETTER-SPACING: 0.1pt">ADO 2.1</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">引入了断开连接的记录集，允许从数据库中检索数据，把它们传送给客户机，进行处理，再重新连接服务器。但它们使用起来常常很繁琐，因为断开连接的工作方式不是一开始就设计好的。</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">ADO.NET</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">类则不同，除了一种情况</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">(<provider></span><span lang="EN-US"> DataReader<span style="LETTER-SPACING: 0.1pt">)</span></span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">外，它们都用于脱机处理数据库。</span></p>
<p class="a3" style="MARGIN-TOP: 8.15pt; FTEL: 21.45pt"><span style="FONT-FAMILY: 黑体">注意：</span></p>
<p class="a1" style="FTEL: 21.45pt"><span style="FONT-FAMILY: 楷体_GB2312">本章将介绍在</span><span lang="EN-US">.NET Framework</span><span style="FONT-FAMILY: 楷体_GB2312">中用于数据访问的类和接口，主要论述连接数据库时使用的</span><span lang="EN-US">SQL</span><span style="FONT-FAMILY: 楷体_GB2312">类，因为</span><span lang="EN-US">Framework SDK</span><span style="FONT-FAMILY: 楷体_GB2312">示例安装了一个</span><span lang="EN-US">MSDE</span><span style="FONT-FAMILY: 楷体_GB2312">数据库</span><span lang="EN-US">(SQL Server)</span><span style="FONT-FAMILY: 楷体_GB2312">。在大多数情况下，</span><span lang="EN-US">OleDb</span><span style="FONT-FAMILY: 楷体_GB2312">、</span><span lang="EN-US">Oracle</span><span style="FONT-FAMILY: 楷体_GB2312">和</span><span lang="EN-US">ODBC</span><span style="FONT-FAMILY: 楷体_GB2312">类类似于</span><span lang="EN-US">SQL</span><span style="FONT-FAMILY: 楷体_GB2312">代码。</span></p></div>
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<div style='float:left;width:49%'>·<a href='100165592.htm'>21.1 ADO.NET概述</a></div><div style='float:right;width:49%'>·<a href='100165593.htm'>21.1.1 命名空间</a></div><div style='float:left;width:49%'>·<a href='100165594.htm'>21.1.2 共享类</a></div><div style='float:right;width:49%'>·<a href='100165596.htm'>21.2 使用数据库连接</a></div><div style='float:left;width:49%'>·<a href='100165597.htm'>21.2.1 高效地使用连接</a></div><div style='float:right;width:49%'>·<a href='100165598.htm'>21.2.2 事务处理</a></div></div>
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