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<p class="MsoNormal" style="TEXT-ALIGN: left" align="left"><span lang="EN-US">&nbsp;</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">如果要搜索一个元字符，也可以通过带有反斜杠的转义字符来表示。例如，</span><span lang="EN-US">.(</span><span style="FONT-FAMILY: 宋体">一个句点</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">表示除了换行字符以外的任何字符，而</span><span lang="EN-US">\.</span><span style="FONT-FAMILY: 宋体">表示一个点。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.3pt">可以把可替换的字符放在方括号中，请求匹配包含这些字符。例如，</span><span lang="EN-US">[1|c]</span><span style="FONT-FAMILY: 宋体">表示字符可以是</span><span lang="EN-US">l</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">c</span><span style="FONT-FAMILY: 宋体">。如果要搜索</span><span lang="EN-US">map</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">man</span><span style="FONT-FAMILY: 宋体">，可以使用序列</span><span lang="EN-US">ma[n|p]</span><span style="FONT-FAMILY: 宋体">。在方括号中，也可以指定一个范围，例如</span><span lang="EN-US">[a-z]</span><span style="FONT-FAMILY: 宋体">表示所有的小写字母，</span><span lang="EN-US">[A-E]</span><span style="FONT-FAMILY: 宋体">表示</span><span lang="EN-US">A</span><span style="FONT-FAMILY: 宋体">到</span><span lang="EN-US">E</span><span style="FONT-FAMILY: 宋体">之间的所有大写字母，</span><span lang="EN-US">[0-9]</span><span style="FONT-FAMILY: 宋体">表示一个数字。如果要搜索一个整数</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">该序列只包含</span><span lang="EN-US">0</span><span style="FONT-FAMILY: 宋体">到</span><span lang="EN-US">9</span><span style="FONT-FAMILY: 宋体">的字符</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，就可以编写</span><span lang="EN-US">[0-9]+(</span><span style="FONT-FAMILY: 宋体">注意，使用</span><span lang="EN-US">+</span><span style="FONT-FAMILY: 宋体">字符表示至少要有这样一个数字，但可以有多个数字，所以</span><span lang="EN-US">9</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US"> 83</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US"> 854</span><span style="FONT-FAMILY: 宋体">等都是匹配的</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">。</span></p>
<h3 style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 8.15pt"><a ftel="_Toc507815070"><span lang="EN-US">8.2.3 &nbsp;</span></a><span style="FONT-FAMILY: 黑体">显示结果</span></h3>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">本节编写一个示例</span><span lang="EN-US">RegularExpressionsPlayaround</span><span style="FONT-FAMILY: 宋体">，看看正则表达式的工作方式。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">该示例的核心是一个方法</span><span lang="EN-US">WriteMatches()</span><span style="FONT-FAMILY: 宋体">，它把</span><span lang="EN-US">MatchCollection</span><span style="FONT-FAMILY: 宋体">中的所有匹配以比较详细的方式显示出来。对于每个匹配，它都会显示该匹配在输入字符串中所在的索引、匹配的字符串和一个略长的字符串，其中包含匹配和输入文本中至多</span><span lang="EN-US">10</span><span style="FONT-FAMILY: 宋体">个外围字符，其中至多有</span><span lang="EN-US">5</span><span style="FONT-FAMILY: 宋体">个字符放在匹配的前面，至多</span><span lang="EN-US">5</span><span style="FONT-FAMILY: 宋体">个字符放在匹配的后面</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">如果匹配的位置在输入文本的开头或结尾</span><span lang="EN-US">5</span><span style="FONT-FAMILY: 宋体">个字符内，则结果中匹配前后的字符就会少于</span><span lang="EN-US">5</span><span style="FONT-FAMILY: 宋体">个</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">。换言之，如果要匹配的单词是</span><span lang="EN-US">messaging</span><span style="FONT-FAMILY: 宋体">，靠近输入文本末尾的匹配应是&ldquo;</span><span lang="EN-US">and messaging of d</span><span style="FONT-FAMILY: 宋体">&rdquo;，匹配的前后各有</span><span lang="EN-US">5</span><span style="FONT-FAMILY: 宋体">个字符，但位于输入文本的最后一个字上的匹配就应是</span><span lang="EN-US">&quot;g of data&quot; </span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1.5pt">&mdash;&mdash;</span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">匹配的后面只有一个字符。因为在该字符的后面是字符串的结尾。这个长字符串可以更清楚地表明正则表达式是在什么地方查找到匹配的：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">static void WriteMatches(string text, MatchCollection matches)</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">&nbsp;&nbsp; Console.WriteLine(&quot;Original text was: \n\n&quot; + text + &quot;\n&quot;);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; Console.WriteLine(&quot;No. of matches: &quot; + matches.Count);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; foreach (Match nextMatch in matches)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; int Index = nextMatch.Index;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; string result = nextMatch.ToString();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;int charsBefore = (Index &lt; 5) ? Index : 5;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; int fromEnd = text.Length - Index - result.Length;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; int charsAfter = (fromEnd &lt; 5) ? fromEnd : 5;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; int charsToDisplay = charsBefore + charsAfter + result.Length;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Console.WriteLine(&quot;Index: {0}, \tString: {1}, \t{2}&quot;,</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Index, result,</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; text.Substring(Index - charsBefore, charsToDisplay));</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在这个方法中，处理过程是确定在较长的子字符串中有多少个字符可以显示，而无需超限输入文本的开头或结尾。注意在</span><span lang="EN-US">Match</span><span style="FONT-FAMILY: 宋体">对象上使用了另一个属性</span><span lang="EN-US">Value</span><span style="FONT-FAMILY: 宋体">，它包含标识该匹配的字符串。而且，</span><span lang="EN-US">RegularExpressionsPlayaround</span><span style="FONT-FAMILY: 宋体">只包含名为</span><span lang="EN-US">Find1</span><span style="FONT-FAMILY: 宋体">、</span><span lang="EN-US">Find2</span><span style="FONT-FAMILY: 宋体">等的方法，这些方法根据本节中的示例执行某些搜索操作。例如，</span><span lang="EN-US">Find2</span><span style="FONT-FAMILY: 宋体">在字开头处查找以</span><span lang="EN-US">a</span><span style="FONT-FAMILY: 宋体">开头的字符串：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">static void Find2()</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 32.25pt"><span lang="EN-US">string Text = </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 32.25pt"><span lang="EN-US">@&quot;This comprehensive compendium provides a broad and thorough investigation of all</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 32.25pt"><span lang="EN-US">aspects of programming with ASP.NET. Entity revised and updated for the 1.1 </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 32.25pt"><span lang="EN-US">Release of .NET, this book will give you the information you need to master ASP.NET</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 32.25pt"><span lang="EN-US">And build a dynamic, successful, enterprise Web application.&rdquo;;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; string pattern = @&quot;\ba&quot;;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; MatchCollection matches = Regex.Matches(text, pattern, </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp; RegexOptions.IgnoreCase);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; WriteMatches(text, matches);</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal" style="FTEL: 0cm"><span style="FONT-FAMILY: 宋体">这是一个简单的</span><span lang="EN-US">Main()</span><span style="FONT-FAMILY: 宋体">方法，可以从中编辑并选择一个</span><span lang="EN-US">Find&lt;n&gt;()</span><span style="FONT-FAMILY: 宋体">方法：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">static void Main()</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">&nbsp;&nbsp; Find1();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; Console.ReadLine();</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal" style="FTEL: 0cm"><span style="FONT-FAMILY: 宋体">这段代码还使用了命名空间</span><span lang="EN-US">RegularExpressions</span><span style="FONT-FAMILY: 宋体">：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">using System;</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">using System.Text.RegularExpressions;</span></p>
<p class="MsoNormal" style="FTEL: 0cm"><span style="FONT-FAMILY: 宋体">运行带有</span><span lang="EN-US">Find1()</span><span style="FONT-FAMILY: 宋体">方法的示例，得到如下所示的结果：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><strong><span lang="EN-US">RegularExpressionsPlayaround</span></strong></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">Original text was:</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">This comprehensive compendium provides a broad and thorough investigation of all</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">aspects of programming with ASP.NET. Entity revised and updated for the 1.1 </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">Release of .NET, this book will give you the information you need to master ASP.NET</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">And build a dynamic, successful, enterprise Web application.</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">&nbsp;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US">No. of matches: 1</span></p>
<p class="a6" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Index: 291,&nbsp;&nbsp;&nbsp;&nbsp; String: application,&nbsp;&nbsp;&nbsp; Web application. </span></p>
<h3 style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 8.15pt"><a ftel="_Toc507815071"><span lang="EN-US">8.2.4 &nbsp;</span></a><span style="FONT-FAMILY: 黑体">匹配、组合和捕获</span></h3>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span style="FONT-FAMILY: 宋体">正则表达式的一个很好的特性是可以把字符组合起来，其方式与</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">中的复合语句一样。在</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">中，可以把任意数量的语句放在花括号中，把它们组合在一起。其结果就像一个复合语句那样。在正则表达式模式中，也可以把任何字符组合起来</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">包括元字符和转义序列</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，像处理一个字符那样处理它们。惟一的区别是要使用圆括号，而不是花括号，得到的序列称为一个组。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span style="FONT-FAMILY: 宋体">例如，模式</span><span lang="EN-US">(an)+</span><span style="FONT-FAMILY: 宋体">定位序列</span><span lang="EN-US">an</span><span style="FONT-FAMILY: 宋体">的任意重复。量词</span><span lang="EN-US">+</span><span style="FONT-FAMILY: 宋体">只应用于它前面的一个字符，但因为我们把字符组合起来了，所以它现在把重复的</span><span lang="EN-US">an</span><span style="FONT-FAMILY: 宋体">作为一个单元来对待。</span><span lang="EN-US">(an)+</span><span style="FONT-FAMILY: 宋体">应用到输入文本</span><span lang="EN-US">&quot;bananas came to Europe late in the annals of history&quot;</span><span style="FONT-FAMILY: 宋体">上，会从</span><span lang="EN-US">bananas</span><span style="FONT-FAMILY: 宋体">中选择出</span><span lang="EN-US">anan</span><span style="FONT-FAMILY: 宋体">。另一方面，如果使用</span><span lang="EN-US">an+</span><span style="FONT-FAMILY: 宋体">，则将从</span><span lang="EN-US">annals</span><span style="FO