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            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">out</span></p>
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            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">struct</span></p>
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            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">while</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 81.4pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="109">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">decimal</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 68.6pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="91">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">goto</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 77.95pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="104">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">override</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 97.35pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="130">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">switch</span></p>
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            <td style="BORDER-RIGHT: medium none; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 99.95pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="133">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">&nbsp;</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 81.4pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="109">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">default</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 68.6pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="91">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">if</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 77.95pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="104">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">params</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 97.35pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="130">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">this</span></p>
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            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">&nbsp;</span></p>
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            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">delegate</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 68.6pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="91">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Implicit</span></p>
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            <td style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 9.9pt; BORDER-TOP: medium none; PADDING-LEFT: 9.9pt; PADDING-BOTTOM: 1.4pt; BORDER-LEFT: medium none; WIDTH: 77.95pt; PADDING-TOP: 1.4pt; BORDER-BOTTOM: windowtext 1pt solid" valign="top" width="104">
            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">private</span></p>
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            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">throw</span></p>
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            <p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">&nbsp;</span></p>
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<p class="MsoNormal"><span lang="EN-US">&nbsp;</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">如果需要把某一保留字用作标识符</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">例如，访问一个用另一种语言编写的类</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，可以在标识符的前面加上前缀</span><span lang="EN-US">@</span><span style="FONT-FAMILY: 宋体">符号，指示编译器其后的内容是一个标识符，而不是</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">关键字</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">所以</span><span lang="EN-US">abstract</span><span style="FONT-FAMILY: 宋体">不是有效的标识符，而</span><span lang="EN-US">@abstract</span><span style="FONT-FAMILY: 宋体">是</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">最后，标识符也可以包含</span><span lang="EN-US">Unicode</span><span style="FONT-FAMILY: 宋体">字符，用语法</span><span lang="EN-US">\uXXXX</span><span style="FONT-FAMILY: 宋体">来指定，其中</span><span lang="EN-US">XXXX</span><span style="FONT-FAMILY: 宋体">是</span><span lang="EN-US">Unicode</span><span style="FONT-FAMILY: 宋体">字符的四位</span><span lang="EN-US">16</span><span style="FONT-FAMILY: 宋体">进制代码。下面是有效标识符的一些例子：</span></p>
<p class="a6" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">●</span><span lang="EN-US" style="FONT-FAMILY: 宋体"> </span><span lang="EN-US">Name</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">●</span><span lang="EN-US" style="FONT-FAMILY: 宋体"> </span><span lang="EN-US" style="FONT-SIZE: 10.5pt">u</span><span lang="EN-US">berflu&szlig;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">●</span><span lang="EN-US" style="FONT-FAMILY: 宋体"> </span><span lang="EN-US">_Identifier</span></p>
<p class="a6" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">●</span><span lang="EN-US" style="FONT-FAMILY: 宋体"> </span><span lang="EN-GB">\u005fIdentifier</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">最后两个标识符是相同的，可以互换</span><span lang="EN-US">(005f</span><span style="FONT-FAMILY: 宋体">是下划线字符的</span><span lang="EN-US">Unicode</span><span style="FONT-FAMILY: 宋体">代码</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">，所以在相同的作用域内不要声明两次。注意虽然从语法上看，标识符中可以使用下划线字符，但在大多数情况下，最好不要这么做，因为它不符合</span><span lang="EN-US">Microsoft</span><span style="FONT-FAMILY: 宋体">的变量命名规则，这种命名规则可以确保开发人员使用相同的命名规则，易于阅读每个人编写的代码。</span></p>
<h3 style="MARGIN: 8.15pt 0cm"><span><span lang="EN-US">2.14.2&nbsp; </span></span><span style="FONT-FAMILY: 黑体">用法</span><span style="FONT-FAMILY: 黑体">约定</span></h3>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.1pt">在任何开发环境中，通常有一些传统的编程风格。这些风格不是语言的一部分，而是约定，例如，变量如何命名，类、方法或函数如何使用等。如果使用某语言的大多数开发人员都遵循相同的约定，不同的开发人员就很容易理解彼此的代码，有助于程序的维护。例如，</span><span lang="EN-US" style="LETTER-SPACING: -0.1pt">Visual Basic 6</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.1pt">的一个公共</span><span lang="EN-US" style="LETTER-SPACING: -0.1pt">(</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -0.1pt">但不统</span><span style="FONT-FAMILY: 宋体">一</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">约定是，表示字符串的变量名以小写字母</span><span lang="EN-US">s</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US">str</span><span style="FONT-FAMILY: 宋体">开头，如</span><span lang="EN-US">Dim sResult As String</span><span style="FONT-FAMILY: 宋体">或</span> <span lang="EN-US">Dim strMessage As String</span><span style="FONT-FAMILY: 宋体">。约定主要取决于语言和环境。例如，在</span><span lang="EN-US">Windows</span><span style="FONT-FAMILY: 宋体">平台上编程的</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 宋体">开发人员一般使用前缀</span><span lang="EN-US">psz</span><span style="FONT-FAMILY: 宋体">或</span><span lang="EN-US"> lpsz</span><span style="FONT-FAMILY: 宋体">表示字符串：</span><span lang="EN-US">char *pszResult; char *lpszMessage;</span><span style="FONT-FAMILY: 宋体">，但在</span><span lang="EN-US">UNIX</span><span style="FONT-FAMILY: 宋体">机器上，则不使用任何前缀：</span><span lang="EN-US">char *Result; char *Message;</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">从本书中的示例代码中可以总结出，</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">中的约定是命名变量时不使用任何前缀：</span><span lang="EN-US">string Result; string Message;</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="a3" style="MARGIN-TOP: 8.15pt; TEXT-INDENT: 21.45pt"><span style="FONT-FAMILY: 黑体">注意：</span></p>
<p class="a1" style="MARGIN-BOTTOM: 8.15pt; TEXT-INDENT: 21.45pt"><span style="FONT-FAMILY: 楷体_GB2312">用带有前缀字母的变量名来表示某个数据类型，这种约定称为</span><span lang="EN-US">Hungarian</span><span style="FONT-FAMILY: 楷体_GB2312">表示法。这样，其他阅读该代码的开发人员就可以立即从变量名中了解它代表什么数据类型。在有了智能编辑器和</span><span lang="EN-US">IntelliSense</span><span style="FONT-FAMILY: 楷体_GB2312">之后，人们普遍认为</span><span lang="EN-US">Hungarian</span><span style="FONT-FAMILY: 楷体_GB2312">表示法是多余的。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">但是，在许多语言中，用法约定是从语言的使用过程中逐渐演变而来的，</span><span lang="EN-US">Microsoft</span><span style="FONT-FAMILY: 宋体">编写的</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">和整个</span><span lang="EN-US">.NET Framework</span><span style="FONT-FAMILY: 宋体">都有非常多的用法约定，详见</span><span lang="EN-US">.NET/C# MSDN</span><span style="FONT-FAMILY: 宋体">文档说明。这说明，从一开始，</span><span lang="EN-US">.NET</span><span style="FONT-FAMILY: 宋体">程序就有非常高的互操作性，开发人员可以以此来理解代码。用法规则还得益于</span><span lang="EN-US">20</span><span style="FONT-FAMILY: 宋体">年来面向对象编程的发展，因此相关的新闻组已经仔细考虑了这些用法规则，而且已经为开发人员团体所接受。所以我们应遵守这些约定。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">但要注意，这些规则与语言规范是不同的。用户应尽可能遵循这些规则。但如果有很好的理由不遵循它们，也不会有什么问题。例如，不遵循这些用法约定，也不会出现编译错误。一般情况下，如果不遵循用法规则，就必须有一个说得过去的理由。规则应是一个正确的决策，而不是让人头痛的东西。在阅读本书的后续内容时，应注意到在本书的许多示例中，都没有遵循该约定，这通常是因为某些规则适用于大型程序，而不适合于本书中的小示例。如果编写一个完整的软件包，就应遵循这些规则，但它们并不适合于只有</span><span lang="EN-US">20</span><span style="FONT-FAMILY: 宋体">行代码的独立程序。在许多情况下，遵循约定会使这些示例难以理解。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">编程风格的规则非常多。这里只介绍一些比较重要的规则，以及最适合于用户的规则。如果用户要让代码完全遵循用法规则，就需要参考</span><span lang="EN-US">MSDN</span><span style="FONT-FAMILY: 宋体">文档说明。</span></p>
<h4 style="TEXT-INDENT: 21.45pt"><span><span lang="EN-US">1. </span></span><span style="FONT-FAMILY: 黑体">命名约定</span></h4>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">使程序易于理解的一个重要方面是给对象选择命名的方式，包括变量名、方法名、类名、枚举名和命名空间的名称。</span></p>
<p class="MsoNormal"><span style="COLOR: black; FONT-FAMILY: 宋体">显然，这些名称应反映对象的功能，且不与其他名称冲突。在</span><span lang="EN-US" style="COLOR: black">.NET Framework</span><span style="COLOR: black; FONT-FAMILY: 宋体">中，一般规则也是变量名要反映变量实例的功能，而不是反映数据类型。例如，</span><span lang="EN-US" style="COLOR: black">Height</span><span style="COLOR: black; FONT-FAMILY: 宋体">就是一个比较好的变量名，而</span><span lang="EN-US" style="COLOR: black">IntegerValue</span><span style="COLOR: black; FONT-FAMILY: 宋体">就不太好。但是，这种规则是一种理想状态，很难<span style="LETTER-SPACING: -0.3pt">达到。在处理控件时，大多数情况下使用</span></span><span lang="EN-US" style="COLOR: black; LETTER-SPACING: -0.3pt">ConfirmationDialog </span><span style="COLOR: black; FONT-FAMILY: 宋体; LETTER-SPACING: -0.3pt">和</span><span lang="EN-US" style="COLOR: black"> ChooseEmployeeListBox</span><span style="COLOR: black; FONT-FAMILY: 宋体">等变量名比较好，这些变量名说明了变量的数据类型。</span></p>
<p class="MsoNormal"><span style="COLOR: black; FONT-FAMILY: 宋体">名称的约定包括以下几个方面：</span></p>
<p class="a3" style="MARGIN-TOP: 8.15pt; TEXT-INDENT: 21.45pt"><span lang="EN-US">(1) </span><span style="FONT-FAMILY: 黑体">名称的大小写</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在许多情况下，名称都应使用</span><span lang="EN-US">Pascal</span><span style="FONT-FAMILY: 宋体">大小写命名形式。</span><span lang="EN-US"> Pascal </span><span style="FONT-FAMILY: 宋体">大小写形式是指名称中单词的第一个字母大写：</span><span lang="EN-US"> EmployeeSalary, ConfirmationDialog, PlainTextEncoding</span><span style="FONT-FAMILY: 宋体">。注意，命名空间、类、以及基类中的成员等的名称都应遵循该规则，最好不要使用带有下划线字符的单词，即名称不应是</span><span lang="EN-US">employee_salary</span><span style="FONT-FAMILY: 宋体">。其他语言中常量的名称常常全部都是大写，但在</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">中最好不要这样，因为这种名称很难阅读，而应全部使用</span><span lang="EN-US">Pascal </span><span style="FONT-FAMILY: 宋体">大小写形式的命名约定：</span></p>
<p class="2" style="MARGIN: 8.15pt 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; const int MaximumLength;</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">我们还推荐使用另一种大小写模式：</span><span lang="EN-US">camel</span><span style="FONT-FAMILY: 宋体">大小写形式。这种形式类似于</span><span lang="EN-US">Pascal </span><span style="FONT-FAMILY: 宋体">大小写形式，但名称中第一个单词的第一个字母不是大写：</span><span lang="EN-US">employeeSalary, confirmationDialog, plainTextEncoding</span><span style="FONT-FAMILY: 宋体">。有三种情况可以使用</span><span lang="EN-US">camel</span><span style="FONT-FAMILY: 宋体">大小写形式。</span></p>