100165600.htm
来自「C#高级编程(第三版),顶死你们。。 。up」· HTM 代码 · 共 192 行 · 第 1/2 页
HTM
192 行
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head><title>
21.3.1 执行命令
</title></head>
<body>
<div class="area">
<div class="col1">
<div class="lineBlue">
</div>
<!-- title -->
<div class="arcTitle">
<h1>
<a href="../16">
C#高级编程（第3版）
</a>
</h1>
<div style="text-align: center; font-size: 15px">
<a href="100165600.htm">
21.3.1 执行命令
</a>
</div>
<div style="text-align: center; font-size: 15px">
<a class="url" href="../../default.htm">http://book.csdn.net/</a>
2006-10-13 14:41:00
</div>
<div style="margin: 0px auto; width: 700px; border: solid 1px #0b5f98;">
<div style="float: left; width: 16px; background-color: #0b5f98; color: White; padding: 1px;">
图书导读
</div>
<div style="float: right; width: 670px; text-align: left; line-height: 16pt; padding-left: 2px">
<!--导读-->
<h1 id="divCurrentNode" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165600.htm'><font color='red'>21.3.1 执行命令</font></a></h1>
<div id="divRelateNode" style="padding-left: 2px">
<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 style='float:left;width:49%'>·<a href='100165599.htm'>21.3 命令</a></div><div style='float:right;width:49%'>·<a href='100165601.htm'>21.3.2 调用存储过程</a></div><div style='float:left;width:49%'>·<a href='100165602.htm'>21.4 快速数据访问：数据读取器</a></div><div style='float:right;width:49%'>·<a href='100165603.htm'>21.5 管理数据和关系：DataSet类</a></div></div>
</div>
</div>
</div>
<!-- main -->
<div id="main">
<div id="text">
<div id="csdn_zhaig_ad_yahoo_2"></div>
<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="_Toc507815161"><span lang="EN-GB">21.3.1 </span></a><span style="FONT-FAMILY: 黑体">执行命令</span></h3>
<p class="MsoNormal" style="LINE-HEIGHT: 18pt"><a ftel="OleDbCommandmethods"><span style="FONT-FAMILY: 宋体">定义好命令后，就需要执行它们。执行语句有许多方式，这取决于要从命令中返回什么数据。</span></a><span lang="EN-GB"><provider></span><span lang="EN-US">Command</span><span style="FONT-FAMILY: 宋体">类提供了下述可执行的命令：</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">ExecuteNonQuery()</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">执行一个命令，但不返回任何结果。</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">ExecuteReader ()</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">执行一个命令，返回一个类型化的</span><span lang="EN-US">IDataReader</span><span style="FONT-FAMILY: 宋体">。</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">ExecuteScalar ()</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">执行一个命令，返回一个值。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 18pt"><span style="FONT-FAMILY: 宋体">除了上述命令外，</span><span lang="EN-US">SqlCommand</span><span style="FONT-FAMILY: 宋体">类也提供了下面的方法：</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">ExecuteXmlReader()</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">——</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">执行一个命令，返回一个</span><span lang="EN-US"> XmlReader</span><span style="FONT-FAMILY: 宋体">对象，它可以用于传送从数据库中返回的</span><span lang="EN-US">XML</span><span style="FONT-FAMILY: 宋体">代码段。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 18pt"><span style="FONT-FAMILY: 宋体">与其他章节一样，可以从</span><span lang="EN-US">Wrox</span><span style="FONT-FAMILY: 宋体">网站</span><span lang="EN-US">www.wrox.com</span><span style="FONT-FAMILY: 宋体">上下载本节的示例代码。</span></p>
<h4 style="FTEL: 21.45pt"><span lang="EN-GB">1.</span><span lang="EN-GB" style="FONT-FAMILY: 宋体"> </span><span lang="EN-GB">ExecuteNonQuery()</span><span style="FONT-FAMILY: 黑体">方法</span></h4>
<p class="MsoNormal" style="LINE-HEIGHT: 17pt"><a ftel="ExecuteNonQuery"><span style="FONT-FAMILY: 宋体">这个方法一般用于</span><span lang="EN-US">UPDATE</span></a><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US"> INSERT</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US"> DELETE</span><span style="FONT-FAMILY: 宋体">语句，惟一的返回值是受影响的记录个数。但如果调用一个有输出参数的存储过程，该方法就有返回值：</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;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB">using System.Data.SqlClient;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB">public class ExecuteNonQueryExample</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> public static void Main(string[] args)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> string source = "server=(local)\\NetSDK;" +</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> "</span><span lang="EN-GB"> </span><span lang="EN-GB">integrated security=SSPI;" + </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> "database=Northwind";</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> string select = "UPDATE Customers " + </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> "SET ContactName = 'Bob' " +</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> "WHERE ContactName = 'Bill'";</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> SqlConnection conn = new SqlConnection(source);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> conn.Open();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> SqlCommand cmd = new SqlCommand(select, conn);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> int rowsReturned = cmd.ExecuteNonQuery();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> Console.WriteLine("{0} rows returned.", rowsReturned);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> conn.Close();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; 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">}</span></p>
<p class="MsoNormal"><span lang="EN-US">ExecuteNonQuery()</span><span style="FONT-FAMILY: 宋体">返回命令所操作的行数</span><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">它为一整数。</span></p>
<h4 style="FTEL: 21.45pt"><span lang="EN-GB">2.</span><span lang="EN-GB" style="FONT-FAMILY: 宋体"> </span><span lang="EN-GB">ExecuteReader()</span><span style="FONT-FAMILY: 黑体">方法</span></h4>
<p class="MsoNormal"><a ftel="SqlCommandmethods"></a><a ftel="ExecuteReader"><span style="FONT-FAMILY: 宋体">这个方法执行命令</span></a><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">根据使用的提供程序返回一个类型化的</span><span lang="EN-US">DataReader</span><span style="FONT-FAMILY: 宋体">对象</span><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">返回的对象可以用于迭代返回的记录</span><span style="FONT-FAMILY: 宋体">，</span><span style="FONT-FAMILY: 宋体">如下面的代码所示。图</span><span lang="EN-US">21-2</span><span style="FONT-FAMILY: 宋体">显示了这段代码的结果。</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-GB">using System;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB">using System.Data.SqlClient;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB">public class ExecuteReaderExample</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB">{</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> public static void Main(string[] args)</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> {</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> string source = "server=(local)\\NetSDK;" +</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> "</span><span lang="EN-GB"> </span><span lang="EN-GB">integrated security=SSPI;" + </span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> "database=Northwind";</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> string select = "SELECT ContactName,CompanyName FROM Customers";</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> SqlConnection conn = new SqlConnection(source);</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> conn.Open();</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> SqlCommand cmd = new SqlCommand(select, conn);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 14.5pt; FTEL: 18.45pt"><span lang="EN-GB"> </span><span lang="EN-US">SqlDataReader reader = cmd.ExecuteReader();</span></p>
⌨️ 快捷键说明
复制代码Ctrl + C
搜索代码Ctrl + F
全屏模式F11
增大字号Ctrl + =
减小字号Ctrl + -
显示快捷键?