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10.2.1 System.Type类
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10.2.1 System.Type类
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2006-10-13 14:41:00
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<div style='float:left;width:49%'>·<a href='100165365.htm'>10.1.1 编写定制特性</a></div><div style='float:right;width:49%'>·<a href='100165366.htm'>10.1.2 定制特性示例WhatsNewAttributes</a></div><div style='float:left;width:49%'>·<a href='100165367.htm'>10.2 反射</a></div><div style='float:right;width:49%'>·<a href='100165369.htm'>10.2.2 TypeView示例</a></div><div style='float:left;width:49%'>·<a href='100165370.htm'>10.2.3 Assembly类</a></div><div style='float:right;width:49%'>·<a href='100165371.htm'>10.2.4 完成WhatsNewAttributes示例</a></div></div>
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<div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><h3 style="MARGIN-TOP: 11.4pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 11.4pt"><a ftel="_Toc507815080"><span lang="EN-US">10.2.1 System.Type</span></a><span style="FONT-FAMILY: 黑体">类</span></h3>
<p class="MsoNormal"><a ftel="Type"><span style="FONT-FAMILY: 宋体">在本书中的许多场合中都使用了</span><span lang="EN-US">Type</span></a><span style="FONT-FAMILY: 宋体">类，但它只存储引用类型：</span></p>
<p class="2" style="MARGIN-TOP: 9.8pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Type t = typeof(double)</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 17pt"><span style="FONT-FAMILY: 宋体">我们以前把</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">看作一个类，但它实际上是一个抽象的基类。只要实例化了一个</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">对象，就实例化了</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">的一个派生类。</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">有与每种数据类型对应的派生类，但一般情况下派生的类只提供各种</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">方法和属性的不同重载，返回对应数据类型的正确数据。一般不增加新的方法或属性。获取指向给定类型的</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">引用有</span><span lang="EN-US">3</span><span style="FONT-FAMILY: 宋体">种常用方式：</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 style="FONT-FAMILY: 宋体">使用</span><span lang="EN-US"> C# </span><span lang="EN-US">typeof </span><span style="FONT-FAMILY: 宋体">运算符，如上所示。这个运算符的参数是类型的名称</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 style="FONT-FAMILY: 宋体">使用</span> <span lang="EN-US"><a ftel="GetType1"></a></span><span lang="EN-US">GetType()</span><span style="FONT-FAMILY: 宋体">方法，所有的类都会从</span><span lang="EN-US">System.Object</span><span style="FONT-FAMILY: 宋体">继承这个类。</span></p>
<p class="2" style="MARGIN-TOP: 9.8pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">double d = 10;</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Type t = d.GetType();</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 17pt"><span style="FONT-FAMILY: 宋体">在一个变量上调用</span><span lang="EN-US">GetType</span><span lang="EN-US">()</span><span style="FONT-FAMILY: 宋体">，而不是把类型的名称作为其参数。但要注意，返回的</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">对象仍只与该数据类型相关：它不包含与类型实例相关的任何信息。如果有一个对象引用，但不能确保该对象实际上是哪个类的实例，这个方法也是很有用的。</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 style="FONT-FAMILY: 宋体">还可以调用</span><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">类的静态方法</span><span lang="EN-US">GetType()</span><a ftel="GetType2"><span style="FONT-FAMILY: 宋体">：</span></a></p>
<p class="2" style="MARGIN-TOP: 9.8pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Type t = Type.GetType("System.Double");</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 17pt"><span lang="EN-US">Type</span><span style="FONT-FAMILY: 宋体">是许多反射技术的入口。它实现许多方法和属性，这里不可能列出所有的方法和属性，而主要介绍如何使用这个类。<span style="LETTER-SPACING: 0.2pt">注意，可用的属性都是只读的：可以使用</span></span><span lang="EN-US" style="LETTER-SPACING: 0.2pt">Type</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">确定数据的类型，但不能使用它修改该类型！</span></p>
<h4 style="MARGIN-TOP: 8pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 21.45pt"><span lang="EN-US">1. Type</span><span style="FONT-FAMILY: 黑体">的属性</span></h4>
<p class="MsoNormal"><a ftel="Typeproperties"><span style="FONT-FAMILY: 宋体">由</span><span lang="EN-US">Type</span></a><span style="FONT-FAMILY: 宋体">执行的属性可以分为下述</span><span lang="EN-US">3</span><span style="FONT-FAMILY: 宋体">类：</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 style="FONT-FAMILY: 宋体">有许多属性都可以获取包含与类相关的各种名称的字符串，如表</span><span lang="EN-US">10-1</span><span style="FONT-FAMILY: 宋体">所示。</span></p>
<p class="a5" style="MARGIN-TOP: 8.15pt"><span style="FONT-FAMILY: 黑体">表</span><span lang="EN-US"> 10-1</span></p>
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<p class="a2"><span style="FONT-FAMILY: 黑体">属</span><span lang="EN-US" style="FONT-FAMILY: 'Times New Roman'"> </span><span style="FONT-FAMILY: 黑体">性</span></p>
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<p class="a2"><span style="FONT-FAMILY: 黑体">返</span><span style="FONT-FAMILY: 'Times New Roman'"> </span><span style="FONT-FAMILY: 黑体">回</span><span style="FONT-FAMILY: 'Times New Roman'"> </span><span style="FONT-FAMILY: 黑体">值</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Name</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span style="FONT-FAMILY: 宋体">数据类型名</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">FullName</span></p>
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