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<p class=MsoNormal><span style='font-family:宋体'>这里不打算介绍给打开文件对话框添加事件处理程序的详细内容，因为它们基本上与前面的</span><span
lang=EN-US>BinaryFileReader</span><span style='font-family:宋体'>示例相同。与这个示例相同，打开一个新文件，将调用</span><span
lang=EN-US>DisplayFile()</span><span style='font-family:宋体'>方法。其惟一的区别是</span><span
lang=EN-US>DisplayFile</span><span style='font-family:宋体'>的执行方式，本例有一个保存文件的选项。这由另一个菜单项</span><span
lang=EN-US>save</span><span style='font-family:宋体'>来表示，这个选项的处理程序调用我们添加到代码中的另一个方法</span><span
lang=EN-US>SaveFile()(</span><span style='font-family:宋体'>注意，这个新文件总是重写原来的文件<span
style='letter-spacing:-1.0pt'>——</span></span><span style='letter-spacing:-1.0pt'>
</span><span style='font-family:宋体'>这个示例没有写入另一个文件的选项</span><span lang=EN-US>)</span><span
style='font-family:宋体'>。</span></p>
<p align=center><span lang=EN-US><img width=209 height=217
src="30/image010.jpg"></span></p>
<p align=center style='FTEL:8.15pt'><span style='font-family:宋体'>图</span><span
lang=EN-US> 30-9</span></p>
<p class=MsoNormal><span style='font-family:宋体'>首先看看</span><span lang=EN-US>SaveFile()</span><span
style='font-family:宋体'>，因为它是最简单的一个函数。首先利用</span><span lang=EN-US>StreamReader.WriteLine()</span><span
style='font-family:宋体'>方法把文本框中的每行文本依次写入</span><span lang=EN-US>StreamWriter</span><span
style='font-family:宋体'>流，并在每行文本的最后加上回车换行符：</span></p>
<p class=2 style='margin-top:8.15pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span
lang=EN-US> void SaveFile()</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>
StreamWriter sw = new StreamWriter(chosenFile, false, </span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
Encoding.Unicode);</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
foreach (string line in textBoxContents.Lines)</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
sw.WriteLine(line);</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
sw.Close();</span></p>
<p class=2 style='margin-top:0cm;margin-right:0cm;FTEL:8.15pt;
margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
}</span></p>
<p class=MsoNormal style='line-height:17.6pt'><span lang=EN-US>chosenFile</span><span
style='font-family:宋体'>是主窗体的一个字符串字段，它包含已经读取的文件的名称</span><span lang=EN-US>(</span><span
style='font-family:宋体'>与前面的示例一样</span><span lang=EN-US>)</span><span
style='font-family:宋体'>。注意在打开流时指定</span><span lang=EN-US>Unicode</span><span
style='font-family:宋体'>编码方式。如果要以其他格式写入文件，则只需要改变该参数的值。如果要把文本追加到文件中，这个构造函数的第二个参数就设置为</span><span
lang=EN-US>true</span><span style='font-family:宋体'>，但本例不是这样。在构造时必须为</span><span
lang=EN-US>StreamWriter</span><span style='font-family:宋体'>设置编码方式，可以使用只读属性</span><span
lang=EN-US>Encoding</span><span style='font-family:宋体'>。</span></p>
<p class=MsoNormal style='line-height:17.6pt'><span style='font-family:宋体'>下面介绍文件的读取方式。读取过程比较复杂，因为我们不知道要读取的文件中包含多少行文本</span><span
lang=EN-US>(</span><span style='font-family:宋体'>换言之，文件中包含多少个</span><span
lang=EN-US>(char)13 – (char)10</span><span style='font-family:宋体'>序列，因为</span><span
lang=EN-US>char(13) –char(10)</span><span style='font-family:宋体'>是行末的回车换行符</span><span
lang=EN-US>)</span><span style='font-family:宋体'>。解决这个问题的方式是，先把文件读入一个</span><span
lang=EN-US>StringCollection</span><span style='font-family:宋体'>类的实例，该类在</span><span
lang=EN-US>System.Collections.Specialized</span><span style='font-family:宋体'>命名空间中，主要用于保存可动态扩展的一组字符串。它的两个方法是我们感兴趣的：把字符串添加到集合中的</span><span
lang=EN-US>Add()</span><span style='font-family:宋体'>和把字符串集合复制到一个数组</span><span
lang=EN-US>(</span><span style='font-family:宋体'>一个</span><span lang=EN-US>System.Array</span><span
style='font-family:宋体'>实例</span><span lang=EN-US>)</span><span
style='font-family:宋体'>中的</span><span lang=EN-US>CopyTo()</span><span
style='font-family:宋体'>。</span><span lang=EN-US>StringCollection</span><span
style='font-family:宋体'>对象的每个元素包含文件中的一行文本。</span></p>
<p class=MsoNormal style='line-height:17.6pt'><a FTEL=StringCollection><span
lang=EN-US>DisplayFile()</span></a><span style='font-family:宋体'>方法调用另一个方法</span><span
lang=EN-US>ReadFileIntoStringCollection()</span><span style='font-family:宋体'>，来读取文件。之后，就知道文件中有多少行文本了。把</span><span
lang=EN-US>StringCollection</span><span style='font-family:宋体'>复制到大小固定的数组中，并把数组中的内容填充到文本框中。在进行复制时，只复制了字符串的引用，没有复制字符串本身，所以该过程的执行效率很高：</span></p>
<p class=MsoNormal style='line-height:17.6pt'><span lang=EN-US> </span></p>
<p class=2 style='margin-top:8.15pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span
lang=EN-US> void DisplayFile()</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>
StringCollection linesCollection = ReadFileIntoStringCollection();</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
string [] linesArray = new string[linesCollection.Count];</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
linesCollection.CopyTo(linesArray, 0);</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
this.textBoxContents.Lines = linesArray;</span></p>
<p class=2 style='margin-top:0cm;margin-right:0cm;FTEL:8.15pt;
margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
}</span></p>
<p class=MsoNormal style='line-height:17.6pt'><span
lang=EN-US>StringCollection.CopyTo()</span><span style='font-family:宋体'>的第二个参数表示目标数组中的下标，我们从该下标指定的位置开始复制集合。</span></p>
<p class=MsoNormal style='line-height:17.6pt'><span style='font-family:宋体'>下面看看</span><span
lang=EN-US>ReadFileIntoStringCollection()</span><span style='font-family:宋体'>方法。使用</span><span
lang=EN-US>StreamReader</span><span style='font-family:宋体'>读取每一行文本。编译时需要计算读取的字符数，以确保不超出文本框的范围：</span></p>
<p class=2 style='margin-top:8.15pt;margin-right:0cm;FTEL:0cm;
margin-left:21.45pt;FTEL:.0001pt;FTEL:18.45pt'><span
lang=EN-US> StringCollection
ReadFileIntoStringCollection()</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>
const int MaxBytes = 65536;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
StreamReader sr = new StreamReader(chosenFile);</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
StringCollection result = new
StringCollection();</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
int nBytesRead = 0;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
string nextLine;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
while ( (nextLine = sr.ReadLine()) != null)</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>
nBytesRead += nextLine.Length;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
if (nBytesRead > MaxBytes)</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
break;</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
result.Add(nextLine);</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>
sr.Close();</span></p>
<p class=2 style='margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
return result;</span></p>
<p class=2 style='margin-top:0cm;margin-right:0cm;FTEL:8.15pt;
margin-left:21.45pt;FTEL:18.45pt'><span lang=EN-US>
}</span></p>
<p class=MsoNormal style='line-height:17.6pt'><span style='font-family:宋体'>这就是该示例的完整代码。</span></p>
<p class=MsoNormal style='line-height:17.6pt'><span style='font-family:宋体'>如果运行</span><span
lang=EN-US>ReadWriteText</span><span style='font-family:宋体'>，读取</span><span
lang=EN-US>NewFile.aspx</span><span style='font-family:宋体'>文件，然后保存它，该文件的格式就是</span><span
lang=EN-US>Unicode</span><span style='font-family:宋体'>。任何常用的</span><span
lang=EN-US>Windows</span><span style='font-family:宋体'>应用程序</span><span
lang=EN-US>(Notepand</span><span style='font-family:宋体'>，</span><span
lang=EN-US>Wordpad)</span><span style='font-family:宋体'>都没有提供这种格式，甚至</span><span
lang=EN-US>ReadWriteText</span><span style='font-family:宋体'>示例也只能在</span><span
lang=EN-US>Windows NT/2000/XP/2003</span><span style='font-family:宋体'>下正确读取和显示文件。因为</span><span
lang=EN-US>Windows 9x</span><span style='font-family:宋体'>不支持</span><span
lang=EN-US>Unicode</span><span style='font-family:宋体'>，像</span><span
lang=EN-US>Notepad</span><span style='font-family:宋体'>这样的应用程序不能识别其他平台上的</span><span
lang=EN-US>Unicode</span><span style='font-family:宋体'>文件</span><span
lang=EN-US>(</span><span style='font-family:宋体'>如果从</span><span lang=EN-US>Wrox
Press</span><span style='font-family:宋体'>网站上下载了这个示例，就可以试试</span><span
lang=EN-US>)</span><span style='font-family:宋体'>。但是，如果使用前面的</span><span
lang=EN-US>ReadBinaryFile</span><span style='font-family:宋体'>示例显示文件，就会立即看出它们的区别，如图</span><span
lang=EN-US>30-10</span><span style='font-family:宋体'>所示。最前面的两个字节表示文件的格式是</span><span
lang=EN-US>Unicode</span><span style='font-family:宋体'>，之后，每个字符都用两个字节来表示。这是非常明显的，因为在这个文件中，每个字符的高位字节都是</span><span
lang=EN-US>0</span><span style='font-family:宋体'>，所以每隔一个字节就显示</span><span
lang=EN-US>x00</span><span style='font-family:宋体'>。</span></p>
<p align=center><span lang=EN-US><img width=377 height=238
src="30/image011.jpg"></span></p>
<p align=center style='FTEL:0cm;FTEL:.0001pt'><span
style='font-family:宋体'>图</span><span lang=EN-US> 30-10</span></p>
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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='100165773.htm'><font color='red'>30.3.3 读写文本文件</font></a></h1>
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<div style='float:left;width:49%'>·<a href='100165770.htm'>30.3 读写文件</a></div><div style='float:right;width:49%'>·<a href='100165771.htm'>30.3.1 流</a></div><div style='float:left;width:49%'>·<a href='100165772.htm'>30.3.2 读写二进制文件</a></div><div style='float:right;width:49%'>·<a href='100165774.htm'>30.4 读写注册表</a></div><div style='float:left;width:49%'>·<a href='100165775.htm'>30.4.1 注册表</a></div><div style='float:right;width:49%'>·<a href='100165776.htm'>30.4.2 .NET注册表类</a></div></div>
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