100165338.htm
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"> 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 = </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"> new DoubleOp(MathsOperations.MultiplyByTwo),</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> new DoubleOp(MathsOperations.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"> </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> for (int i=0 ; i<operations.Length ; i++)</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("Using operations[{0}]:", i);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> ProcessAndDisplayNumber(operations[i], 2.0);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> ProcessAndDisplayNumber(operations[i], 7.94);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> ProcessAndDisplayNumber(operations[i], 1.414);</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"> }</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"> 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"> double result = action(value);</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"> "Value is {0}, result of operation is {1}", value, result);</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">在这段代码中，实例化了一个委托数组</span><span lang="EN-US">DoubleOp (</span><span style="FONT-FAMILY: 宋体">记住，一旦定义了委托类，就基本上可以实例化它的实例，就像处理一般的类那样<span style="LETTER-SPACING: -1pt">——</span></span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">所以把一些委托的实例放在数组中是可以的</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">。该数组的每个元素都初始化为由</span><span lang="EN-US">MathsOperations</span><span style="FONT-FAMILY: 宋体">类执行的不同操作。然后循环这个数组，把每个操作应用到</span><span lang="EN-US">3</span><span style="FONT-FAMILY: 宋体">个不同的值上。这说明了使用委托的一种方式<span style="LETTER-SPACING: -1pt">——</span></span><span style="LETTER-SPACING: -1pt"> </span><span style="FONT-FAMILY: 宋体">把方法组合到一个数组中，这样就可以在循环中调用不同的方法了。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">这段代码的关键代码行是把委托传递给</span><span lang="EN-US">ProcessAndDisplayNumber()</span><span style="FONT-FAMILY: 宋体">方法，例如：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US"> ProcessAndDisplayNumber(operations[i], 2.0);</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">其中传递了委托名，但不带任何参数，假定</span><span lang="EN-US">operations[i]</span><span style="FONT-FAMILY: 宋体">是一个委托，其语法是：</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 lang="EN-US">"operations[i] " </span><span style="FONT-FAMILY: 宋体">表示</span><span lang="EN-US"> "</span><span style="FONT-FAMILY: 宋体">这个委托</span><span lang="EN-US">"</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: -1pt">。</span><span style="FONT-FAMILY: 宋体">换言之，就是委托代表的方法。</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 lang="EN-US">"operations[i](2.0)" </span><span style="FONT-FAMILY: 宋体">表示</span><span lang="EN-US"> "</span><span style="FONT-FAMILY: 宋体">调用这个方法，参数放在括号中</span><span lang="EN-US">"</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span lang="EN-US">ProcessAndDisplayNumber()</span><span style="FONT-FAMILY: 宋体">方法定义为把一个委托作为其第一个参数：</span></p>
<p class="a6" 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="MsoNormal"><span style="FONT-FAMILY: 宋体">在这个方法中，调用：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US"> double result = action(value);</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">这实际上是调用</span><span lang="EN-US">action</span><span style="FONT-FAMILY: 宋体">委托实例封装的方法，其返回结果存储在</span><span lang="EN-US">result</span><span style="FONT-FAMILY: 宋体">中。</span></p>
<p class="MsoNormal" style="FTEL: 42.85pt"><span style="FONT-FAMILY: 宋体">运行这个示例，得到如下所示的结果：</span></p>
<p class="a6" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 9.95pt; MARGIN-RIGHT: 0cm; FTEL: 9.95pt"><strong><span lang="EN-US">SimpleDelegate</span></strong></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Using operations[0]:</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Value is 2, result of operation is 4</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Value is 7.94, result of operation is 15.88</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Value is 1.414, result of operation is 2.828</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">Using operations[1]:</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Value is 2, result of operation is 4</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">Value is 7.94, result of operation is 63.0436</span></p>
<p class="a6" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">Value is 1.414, result of operation is 1.999396</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='100165338.htm'><font color='red'>6.1.2 简单的委托示例</font></a></h1>
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<div style='float:left;width:49%'>·<a href='100165326.htm'>前言</a></div><div style='float:right;width:49%'>·<a href='100165336.htm'>6.1 委托</a></div><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='100165339.htm'>6.1.3 BubbleSorter示例</a></div><div style='float:left;width:49%'>·<a href='100165340.htm'>6.1.4 多播委托</a></div><div style='float:right;width:49%'>·<a href='100165341.htm'>6.2 事件</a></div></div>
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