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<p class="MsoNormal"><span lang="ES">● </span><span style="FONT-FAMILY: 宋体">返回当前选中的文件夹</span></p>
<p class="MsoNormal"><span lang="ES">● </span><span style="FONT-FAMILY: 宋体">提供延迟加载文件结构的功能</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">这应是一个好的起点。把</span><span lang="ES" style="LETTER-SPACING: 0.1pt">TreeView</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.1pt">控件作为新控件的基本控件，就可以满足上述的一个需求。</span></p>
<p class="MsoNormal"><span lang="ES">TreeView</span><span style="FONT-FAMILY: 宋体">控件以层次结构的形式显示数据。它显示的数据描述了列表中的对象，并可以带有图标。单击对象或使用箭头键，就可以扩展和压缩这个列表。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在</span><span lang="ES">Visual Studio .NET</span><span style="FONT-FAMILY: 宋体">中创建一个新的</span><span lang="ES">Windows</span><span style="FONT-FAMILY: 宋体">控件库项目，命名为</span><span lang="ES">FolderTree</span><span style="FONT-FAMILY: 宋体">，删除类</span><span lang="ES">UserControl1</span><span style="FONT-FAMILY: 宋体">，添加一个新类，命名为</span><span lang="ES">FolderTree</span><span style="FONT-FAMILY: 宋体">。因为</span><span lang="ES">FolderTree</span><span style="FONT-FAMILY: 宋体">派生于</span><span lang="ES">TreeView</span><span style="FONT-FAMILY: 宋体">，所以类声明由：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="ES">public class FolderTree</span></p>
<p class="MsoNormal"><span lang="ES">&nbsp;</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">改为：</span></p>
<p class="2" style="MARGIN-TOP: 6.5pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="ES">public class FolderTree : System.Windows.Forms.TreeView</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span style="FONT-FAMILY: 宋体">此时就有了一个功能全面、且能工作的</span><span lang="ES">FolderTree</span><span style="FONT-FAMILY: 宋体">控件了。该控件可以完成</span><span lang="ES">TreeView</span><span style="FONT-FAMILY: 宋体">能完成的所有任务。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span lang="ES">TreeView</span><span style="FONT-FAMILY: 宋体">控件包含一个</span><span lang="ES">TreeNode</span><span style="FONT-FAMILY: 宋体">对象集合。我们不能直接把文件和文件夹加载到控件中，<span style="LETTER-SPACING: 0.2pt">但有两种方式可以把加载的</span></span><span lang="ES" style="LETTER-SPACING: 0.2pt">TreeNode</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">映射到</span><span lang="ES" style="LETTER-SPACING: 0.2pt">TreeView</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">的</span><span lang="ES" style="LETTER-SPACING: 0.2pt">Node</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">集合和它表示的文件与文件夹</span><span style="FONT-FAMILY: 宋体">中。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span style="FONT-FAMILY: 宋体">例如，在处理每个文件夹时，都会创建一个新的</span><span lang="ES">TreeNode</span><span style="FONT-FAMILY: 宋体">对象，</span><span lang="ES">Text</span><span style="FONT-FAMILY: 宋体">属性设置为文件或文件夹的名称。如果在某一刻需要文件或文件夹的其他信息，就必须再次进入磁盘收集该信息，或把与文件或文件夹相关的其他数据存储在</span><span lang="ES">Tag</span><span style="FONT-FAMILY: 宋体">属性中。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span style="FONT-FAMILY: 宋体">另一个方法是创建一个派生于</span><span lang="ES">TreeNode</span><span style="FONT-FAMILY: 宋体">的新类。可以添加新属性和方法，且仍能使用</span><span lang="ES">TreeNode</span><span style="FONT-FAMILY: 宋体">的基本功能。本例就使用这个方法，其设计更为灵活。如果需要新属性，就可以添加它们，无需中断已有的代码。</span></p>
<p class="MsoNormal" style="LINE-HEIGHT: 15pt"><span style="FONT-FAMILY: 宋体">有两类对象必须加载到控件中：文件和文件夹。每类对象都有自己的特性。例如，文件夹有一个</span><span lang="ES">DirectoryInfo</span><span style="FONT-FAMILY: 宋体">对象，它包含了额外的信息，而文件有一个</span><span lang="ES">FileInfo</span><span style="FONT-FAMILY: 宋体">对象。由于有这些区别，所以我们使用两个类来加载</span><span lang="ES">TreeView</span><span style="FONT-FAMILY: 宋体">控件：</span><span lang="ES">FileNode</span><span style="FONT-FAMILY: 宋体">和</span><span lang="ES">FolderNode</span><span style="FONT-FAMILY: 宋体">。在项目中添加这两个类，每个类都派生于</span><span lang="ES">TreeNode</span><span style="FONT-FAMILY: 宋体">。下面是</span><span lang="ES">FileNode</span><span style="FONT-FAMILY: 宋体">的代码：</span></p>
<p class="2" style="MARGIN-TOP: 4.9pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="ES">using System;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">using System.Windows.Forms;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">using System.IO;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">namespace FolderTree</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp; ///&lt;summary&gt;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp; /// Summary description for FileNode.</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp; ///&lt;summary&gt;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp; public class FileNode : System.Windows.Forms.TreeNode</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 27.65pt"><span lang="ES">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; string _fileName =&quot;&quot;;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; FileInfo _info;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; public FileNode(string fileName)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; _fileName = FileName;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; _info = new FileInfo(_fileName);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; base.Text = _info.Name;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; public string FileName</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; LINE-HEIGHT: 13.5pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;get {return _fileName;}</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; set {_fileName = value;}</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; public FileInfo FileNodeInfo</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; get {return _info;}</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp; }</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="ES">}</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">正在处理的文件名被传送给</span><span lang="ES">FileNode</span><span style="FONT-FAMILY: 宋体">的构造函数。在构造函数中，为文件创建</span><span lang="ES">FileInfo</span><span style="FONT-FAMILY: 宋体">对象，并把它设置为成员变量</span><span lang="ES">_info</span><span style="FONT-FAMILY: 宋体">。</span><span lang="EN-US">b</span><span lang="ES">ase.Text</span><span style="FONT-FAMILY: 宋体">属性设置为文件名。由于</span><span lang="ES">FileNode</span><span style="FONT-FAMILY: 宋体">派生于</span><span lang="ES">TreeNode</span><span style="FONT-FAMILY: 宋体">，所以设置</span><span lang="ES">TreeNode</span><span style="FONT-FAMILY: 宋体">的</span><span lang="ES">Text</span><span style="FONT-FAMILY: 宋体">属性，这是显示在</span><span lang="ES">TreeView</span><span style="FONT-FAMILY: 宋体">控件中的文本。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">再添加两个属性来获取数据。</span><span lang="ES" style="LETTER-SPACING: 0.2pt">FileName</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">返回文件名，</span><span lang="ES" style="LETTER-SPACING: 0.2pt">FileNodeInfo</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">返回文件的</span><span lang="ES" style="LETTER-SPACING: 0.2pt">FileInfo</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">对象。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">下面是</span><span lang="ES">FolderNode</span><span style="FONT-FAMILY: 宋体">类的代码。它的结构非常类似于</span><span lang="ES">FileNode</span><span style="FONT-FAMILY: 宋体">，区别是用</span><span lang="ES">DirectoryInfo</span><span style="FONT-FAMILY: 宋体">属性代替了</span><span lang="ES">FileInfo</span><span style="FONT-FAMILY: 宋体">属性，用</span><span lang="ES">FolderPath</span><span style="FONT-FAMILY: 宋体">代替了</span><span lang="ES">FileName</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="ES">using System;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">using System.Windows.Forms;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">using System.IO;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">namespace FolderTree</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp; ///&lt;summary&gt;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp; /// Summary description for DiskObject.</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp; ///&lt;summary&gt;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp; public class FolderNode : System.Windows.Forms.TreeNode</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 27.65pt"><span lang="ES">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp; &nbsp;&nbsp;string _folderPath =&quot;&quot;;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; DirectoryInfo _info;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; public FolderNode (string FolderPath)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; _folderPath = FolderPath;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; _info = new DirectoryInfo (_folderPath);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; this.Text = _info.Name;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; public string FolderPath </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;get {return _folderPath;}</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="ES">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; set {_folderPath = value;}</span></p>