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        2.8  命名空间
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                        2.8  命名空间
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                    2006-8-17 16:57:00
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                <div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><p class="MsoNormal"><span><span style="FONT-FAMILY: 宋体">如前所述,命名空间提供了一种组织相关类和其他类型的方式。与文件或组件不同,命名空间是一种逻辑组合,而不是物理组合。在</span><span lang="EN-US">C#</span></span><span style="FONT-FAMILY: 宋体">文件中定义类时,可以把它包括在命名空间定义中。以后,在定义另一个类,在另一个文件中执行相关操作时,就可以在同一个命名空间中包<span style="LETTER-SPACING: 0.1pt">含它,创建一个逻辑组合,告诉使用类的其他开发人员这两个类是如何相关的以及如何使用它们:</span></span></p>
<p class="2" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">namespace CustomerPhoneBookApp</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; using System;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; public struct Subscriber</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // Code for struct here...</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">把一个类型放在命名空间中,可以有效地给这个类型指定一个较长的名称,该名称包括类型的命名空间,后面是句点</span><span lang="EN-US">(.)</span><span style="FONT-FAMILY: 宋体">和类的名称。在上面的例子中,</span><span lang="EN-US">Subscriber</span><span style="FONT-FAMILY: 宋体">结构的全名是</span><span lang="EN-US" style="LETTER-SPACING: 0.1pt">CustomerPhoneBookApp.Subscriber</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">。这样,有相同短名的不同的类就可以在同一个程序中使用</span><span style="FONT-FAMILY: 宋体">了。</span></p>
<p class="MsoToc1"><span style="FONT-FAMILY: 宋体">也可以在命名空间中嵌套其他命名空间,为类型创建层次结构:</span></p>
<p class="2" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">namespace Wrox</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp; namespace ProCSharp</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; namespace Basics</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; class NamespaceExample</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // Code for the class here...</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt; LINE-HEIGHT: 15pt"><span lang="EN-US">&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 17pt"><span style="FONT-FAMILY: 宋体">每个命名空间名都由它所在命名空间的名称组成,这些名称用句点分隔开,首先是最外层的命名空间,最后是它自己的短名。所以</span><span lang="EN-US">ProfessionalCSharp</span><span style="FONT-FAMILY: 宋体">命名空间的全名是</span><span lang="EN-US">Wrox.ProCSharp</span><span style="FONT-FAMILY: 宋体">,</span><span lang="EN-US">NamespaceExample</span><span style="FONT-FAMILY: 宋体">类的全名是</span><span lang="EN-US">Wrox.ProCSharp.Basics.NamespaceExample</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 17pt"><span style="FONT-FAMILY: 宋体">使用这个语法也可以组织自己的命名空间定义中的命名空间,所以上面的代码也可以写为:</span></p>
<p class="2" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">namespace Wrox.ProCSharp.Basics</span></p>

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