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来自「C#高级编程(第三版),顶死你们。。 。up」· HTM 代码 · 共 135 行 · 第 1/2 页
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<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"> double result = value*2;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> Console.WriteLine(</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> "Multiplying by 2: {0} gives {1}", value, result);</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"> </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> public static void Square(double value)</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"> double result = value*value;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> Console.WriteLine("Squaring: {0} gives {1}", value, result);</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: 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">为了适应这个改变，也必须重写</span><span lang="EN-US">ProcessAndDisplayNumber</span><span style="FONT-FAMILY: 宋体">：</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 ProcessAndDisplayNumber(DoubleOp action, double value)</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"> Console.WriteLine("\nProcessAndDisplayNumber called with value = " +</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> value);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> action(value);</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">下面测试多播委托，其代码如下：</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"> DoubleOp operations = new DoubleOp(MathOperations.MultiplyByTwo);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> operations += new DoubleOp(MathOperations.Square);</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"> ProcessAndDisplayNumber(operations, 2.0);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> ProcessAndDisplayNumber(operations, 7.94);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> ProcessAndDisplayNumber(operations, 1.414);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13pt; FTEL: 18.45pt"><span lang="EN-US"> Console.WriteLine();</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">现在，每次调用</span><span lang="EN-US">ProcessAndDisplayNumber</span><span style="FONT-FAMILY: 宋体">时，都会显示一个信息，说明它已经被调用。然后，下面的语句会按顺序调用</span><span lang="EN-US">action</span><span style="FONT-FAMILY: 宋体">委托实例中的每个方法：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US"> action(value);</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">运行这段代码，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"><a ftel="_Toc507815047"><strong><span lang="EN-US">MulticastDelegate</span></strong></a></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> </span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">ProcessAndDisplayNumber called with value = 2</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Multiplying by 2: 2 gives 4</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Squaring: 2 gives 4</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> </span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">ProcessAndDisplayNumber called with value = 7.94</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Multiplying by 2: 7.94 gives 15.88</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Squaring: 7.94 gives 63.0436</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> </span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">ProcessAndDisplayNumber called with value = 1.414</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Multiplying by 2: 1.414 gives 2.828</span></p>
<p class="a6" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Squaring: 1.414 gives 1.999396</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">如果使用多播委托，就应注意对同一个委托调用方法链的顺序并未正式定义，因此应避免编写依赖于以任意特定顺序调用方法的代码。</span></p></div>
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<h1 id="divCurrentNode2" style="color: #b83507; width: 100%; text-align: left; font-size: 12px; padding-left: 2px">当前章节:<a href='100165340.htm'><font color='red'>6.1.4 多播委托</font></a></h1>
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<div style='float:left;width:49%'>·<a href='100165337.htm'>6.1.1 在C#中使用委托</a></div><div style='float:right;width:49%'>·<a href='100165338.htm'>6.1.2 简单的委托示例</a></div><div style='float:left;width:49%'>·<a href='100165339.htm'>6.1.3 BubbleSorter示例</a></div><div style='float:right;width:49%'>·<a href='100165341.htm'>6.2 事件</a></div><div style='float:left;width:49%'>·<a href='100165342.htm'>6.2.1 从客户的角度讨论事件</a></div><div style='float:right;width:49%'>·<a href='100165343.htm'>6.2.2 生成事件</a></div></div>
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