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<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; Console.WriteLine(i); </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">这里声明了一个</span><span lang="EN-US">int</span><span style="FONT-FAMILY: 宋体">类型的变量</span><span lang="EN-US">i</span><span style="FONT-FAMILY: 宋体">，并把它初始化为</span><span lang="EN-US">0</span><span style="FONT-FAMILY: 宋体">，用作循环计数器。接着测试它是否小于</span><span lang="EN-US">100</span><span style="FONT-FAMILY: 宋体">。因为这个条件等于</span><span lang="EN-US">true</span><span style="FONT-FAMILY: 宋体">，所以执行循环中的代码，显示值</span><span lang="EN-US">0</span><span style="FONT-FAMILY: 宋体">。然后给该计数器加</span><span lang="EN-US">1</span><span style="FONT-FAMILY: 宋体">，再次执行该过程。当</span><span lang="EN-US">i</span><span style="FONT-FAMILY: 宋体">等于</span><span lang="EN-US">100</span><span style="FONT-FAMILY: 宋体">时，循环停止。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">实际上，上述编写循环的方式并不常用。</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">在给变量加</span><span lang="EN-US">1</span><span style="FONT-FAMILY: 宋体">时有一种简化方式，即不使用</span><span lang="EN-US">i = i+1</span><span style="FONT-FAMILY: 宋体">，而简写为</span><span lang="EN-US">i++</span><span style="FONT-FAMILY: 宋体">：</span></p>
<p class="2" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">for (int i = 0; i &lt; 100; i++)</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: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 27.65pt"><span lang="EN-US">//etc.</span></p>
<p class="MsoNormal"><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">的</span><span lang="EN-US">for</span><span style="FONT-FAMILY: 宋体">循环语法比</span><span lang="EN-US">VB</span><span style="FONT-FAMILY: 宋体">中的</span><span lang="EN-US">For<sup>&hellip;</sup>Next</span><span style="FONT-FAMILY: 宋体">循环的功能强大得多，因为迭代程序可以是任何语句。在</span><span lang="EN-US">VB</span><span style="FONT-FAMILY: 宋体">中，只能对循环控制变量加减某个数字。在</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">中，则可以做任何事，例如，让循环控制变量乘以</span><span lang="EN-US">2</span><span style="FONT-FAMILY: 宋体">。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">嵌套的</span><span lang="EN-US">for</span><span style="FONT-FAMILY: 宋体">循环非常常见，在每次迭代外部的循环时，内部循环都要彻底执行完毕。这种模式通常用于在矩形多维数组中遍历每个元素。最外部的循环遍历每一行，内部的循环遍历某行上的每个列。下面的代码可以用作</span><span lang="EN-US">NumberTable</span><span style="FONT-FAMILY: 宋体">例子，显示数字行，它还使用另一个</span><span lang="EN-US">Console</span><span style="FONT-FAMILY: 宋体">方法</span><span lang="EN-US">Console.Write()</span><span style="FONT-FAMILY: 宋体">，该方法的作用与</span><span lang="EN-US">Console.WriteLine()</span><span style="FONT-FAMILY: 宋体">相同，但不在输出中添加回车换行符：</span></p>
<p class="a6" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">using System;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">namespace Wrox.ProCSharp.Basics</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">{</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; class MainEntryPoint</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; {</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; static void Main(string[ ] args)</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&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;&nbsp;&nbsp;&nbsp; // This loop iterates through rows...</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; for (int i = 0; i &lt; 100; i+=10)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><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"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // This loop iterates through columns...</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; for (int j = i; j &lt; i + 10; j++)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&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;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Console.Write(&quot;&nbsp; &quot; + j);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&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;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Console.WriteLine();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; }</span></p>
<p class="a6" 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">尽管</span><span lang="EN-US">j</span><span style="FONT-FAMILY: 宋体">是一个整数，但它会自动转换为字符串，以便进行连接。</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 宋体">开发人员要注意，这比在</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 宋体">中处理字符串容易得多，</span><span lang="EN-US">VB</span><span style="FONT-FAMILY: 宋体">开发人员则已经习惯于此了。</span></p>
<p class="MsoNormal"><span lang="EN-US">C</span><span style="FONT-FAMILY: 宋体">程序员应注意上述例子中的一个特殊功能。在每次迭代后续的外部循环时，最内部循环的计数器变量都要重新声明。这种语法不仅在</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">中可行，在</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 宋体">中也是合法的。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">上述例子的结果是：</span></p>
<p class="a6" style="MARGIN: 8.15pt 0cm 0pt 9.95pt; TEXT-INDENT: 9.95pt"><strong><span lang="EN-US">csc NumberTable.cs</span></strong></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">Microsoft (R) Visual C# .NET Compiler version 7.10.3052.4</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">for Microsoft (R) .NET Framework version 1.1.4322</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">Copyright (C) Microsoft Corporation 2001-2002. All rights reserved.</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 0&nbsp; 1&nbsp; 2&nbsp; 3&nbsp; 4&nbsp; 5&nbsp; 6&nbsp; 7&nbsp; 8&nbsp; 9</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 10&nbsp; 11&nbsp; 12&nbsp; 13&nbsp; 14&nbsp; 15&nbsp; 16&nbsp; 17&nbsp; 18&nbsp; 19</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 20&nbsp; 21&nbsp; 22&nbsp; 23&nbsp; 24&nbsp; 25&nbsp; 26&nbsp; 27&nbsp; 28&nbsp; 29</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 30&nbsp; 31&nbsp; 32&nbsp; 33&nbsp; 34&nbsp; 35&nbsp; 36&nbsp; 37&nbsp; 38&nbsp; 39</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 40&nbsp; 41&nbsp; 42&nbsp; 43&nbsp; 44&nbsp; 45&nbsp; 46&nbsp; 47&nbsp; 48&nbsp; 49</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 50&nbsp; 51&nbsp; 52&nbsp; 53&nbsp; 54&nbsp; 55&nbsp; 56&nbsp; 57&nbsp; 58&nbsp; 59</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 60&nbsp; 61&nbsp; 62&nbsp; 63&nbsp; 64&nbsp; 65&nbsp; 66&nbsp; 67&nbsp; 68&nbsp; 69</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 70&nbsp; 71&nbsp; 72&nbsp; 73&nbsp; 74&nbsp; 75&nbsp; 76&nbsp; 77&nbsp; 78&nbsp; 79</span></p>
<p class="a6" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 80&nbsp; 81&nbsp; 82&nbsp; 83&nbsp; 84&nbsp; 85&nbsp; 86&nbsp; 87&nbsp; 88&nbsp; 89</span></p>
<p class="a6" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp; 90&nbsp; 91&nbsp; 92&nbsp; 93&nbsp; 94&nbsp; 95&nbsp; 96&nbsp; 97&nbsp; 98&nbsp; 99</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">尽管在技术上，可以在</span><span lang="EN-US">for</span><span style="FONT-FAMILY: 宋体">循环的测试条件中计算其他变量，而不计算计数器变量，但这不太常用。也可以在</span><span lang="EN-US">for</span><span style="FONT-FAMILY: 宋体">循环中忽略一个表达式</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">甚或所有表达式</span><span lang="EN-US">)</span><span style="FONT-FAMILY: 宋体">。但此时，要考虑使用</span><span lang="EN-US">while</span><span style="FONT-FAMILY: 宋体">循环。</span></p>
<h4 style="TEXT-INDENT: 21.45pt"><span lang="EN-US">2. while</span><span style="FONT-FAMILY: 黑体">循环</span></h4>
<p class="MsoNormal"><span><span lang="EN-US">while</span></span><span style="FONT-FAMILY: 宋体">循环与</span><span lang="EN-US">C++</span><span style="FONT-FAMILY: 宋体">和</span><span lang="EN-US">Java</span><span style="FONT-FAMILY: 宋体">中的</span><span lang="EN-US">while</span><span style="FONT-FAMILY: 宋体">循环相同，与</span><span lang="EN-US">VB</span><span style="FONT-FAMILY: 宋体">中的</span><span lang="EN-US">While<sup>...</sup>Wend</span><span style="FONT-FAMILY: 宋体">循环相同。与</span><span lang="EN-US">for</span><span style="FONT-FAMILY: 宋体">循环一样，</span><span lang="EN-US">while</span><span style="FONT-FAMILY: 宋体">也是一个预测试的循环。其语法是类似的，但</span><span lang="EN-US">while</span><span style="FONT-FAMILY: 宋体">循环只有一个表达式：</span></p>
<p class="a6" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">while(condition)</span></p>
<p class="a6" style="MARGIN: 0cm 0cm 8.15pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; statement(s);</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">与</span><span lang="EN-US">for</span><span style="FONT-FAMILY: 宋体">循环不同的是，</span><span lang="EN-US">while</span><span style="FONT-FAMILY: 宋体">循环最常用于下述情况：在循环开始前，不知道重复执行一个语句或语句块的次数。通常，在某次迭代中，</span><span lang="EN-US">while</span><span style="FONT-FAMILY: 宋体">循环体中的语句把布尔标记设置为</span><span lang="EN-US">false</span><span style="FONT-FAMILY: 宋体">，结束循环，如下面的例子所示。</span></p>
<p class="2" style="MARGIN: 8.15pt 0cm 0pt 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">bool condition = false;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">while (!condition)</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; // This loop spins until the condition is true</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; DoSomeWork();</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; TEXT-INDENT: 18.45pt"><span lang="EN-US">&nbsp;&nbsp; condition = CheckCondition();&nbsp;&nbsp; // assume CheckCondition() returns a bool</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">所有的</span><span lang="EN-US">C#</span><span style="FONT-FAMILY: 宋体">循环机制，包括</span><span lang="EN-US">while</span><span style="FONT-FAMILY: 宋体">循环，如果只重复执行一条语句，而不是一个语句块，都可以省略花括号。许多程序员都认为最好在任何情况下都加上花括号。</span></p>
<h4 style="TEXT-INDENT: 21.45pt"><span lang="EN-US">3. do<sup>&hellip;</sup>while</span><span style="FONT-FAMILY: 黑体">循环</span></h4>