创建可编辑的xml文档(之四) 删除、改名、插入操作

执行删除、改名、插入操作

   实现了拖放操作就已经完了最难的部分，但是出于完整性考虑，还应该提供一些更好的基本的编辑功能。下面仅仅用四行代码就可以实现删除操作：

[C#]

   string xpath_query = 

      buildXPathQuery(this.SelectedNode);

   System.Xml.XmlNode node = 

      xml_document.DocumentElement.SelectSingleNode(

      xpath_query);

   node.ParentNode.RemoveChild(node);

   SelectedNode.Remove();

   [VB]

   Dim xpath_query As String = _

      buildXPathQuery(Me.SelectedNode)

      Dim node As System.Xml.XmlNode = _

         xml_document.DocumentElement.SelectSingleNode( _

         xpath_query)

      node.ParentNode.RemoveChild(node)

      SelectedNode.Remove()

重命名操作需要更多的一些考虑，你可以调用buildXPathQuery 去查找那个文件夹正在被编辑，还有如何确定是哪一个属性，如何确定被显示名称相应的返回结构的元素或者子元素？这是一个误导的问题，XPath filte函数已经被定义了，你只需应用现面的转换就可以了：

[C#]

   private void XmlTreeView_AfterLabelEdit(object sender, 

      System.Windows.Forms.NodeLabelEditEventArgs e)

   {

      string xpath_query = buildXPathQuery(e.Node);

      System.Xml.XmlNode node = 

         xml_document.DocumentElement.SelectSingleNode(

         xpath_query);

      System.Xml.XmlNode label = 

         node.SelectSingleNode(xpath_filter);

      label.Value = e.Label;

   }   

   [VB]

   Private Sub XmlTreeView_AfterLabelEdit( _

      ByVal sender As Object, _

      ByVal e As 

      System.Windows.Forms.NodeLabelEditEventArgs) _

      Handles MyBase.AfterLabelEdit

      Dim xpath_query As String = buildXPathQuery(e.Node)

      Dim node As System.Xml.XmlNode = _

         xml_document.DocumentElement.SelectSingleNode( _

         xpath_query)

      Dim label As System.Xml.XmlNode = 

         node.SelectSingleNode(xpath_filter)

      label.Value = e.Label

   End Sub

最后一个挑战就是如何按照需求创建一个新的文件夹。query filter 允许用户用一组文件夹而不是xml元素操作xml文档。这样对你想在那些文件夹周围进行移动很有帮助的，而且它还可以告诉在哪里插入一个文件夹，但是它不能告诉你这个文件夹应该包含什么东西，你应该猜测文档中的所有文件夹是否含有相同的结构或者内容。但是我们的目标是创建一个不需要任何预定的显示xml 方法。因此，我选择将这些怎人委托给应用程序控制。例如，客户端代码可以下面这样写：   

[C#]

   System.Xml.XmlDocument insert_fragment = 

      new System.Xml.XmlDocument();

   insert_fragment.LoadXml(

      "<product id='New Item'>" + 

      "<description/><ordercode/><price/>" + 

      "<image/></product>");

   // The TreeView uses XmlInsertionNode to add 

   // a new folder to the tree's underlying XML 

   // document on request

   xmlTreeView1.XmlInsertionNode = 

   insert_fragment.DocumentElement;

   [VB]

   Dim insert_fragment As New System.Xml.XmlDocument()

   insert_fragment.LoadXml(" & _

      "<product id='New Item'>" & _

      "<description/><ordercode/>"<price/>" & _

      "<image/></product>")

   xmlTreeView1.XmlInsertionNode = _

      insert_fragment.DocumentElement

treeview 控件可以缓存一个结构的副本，将它作为一个临时变量来创建一个新的文件夹集合。你所要做的仅仅是确保被定义得文件夹可以被filter query 识别，否则treeview 将不能显示它。因为对于我们操作的文档，xml通常是外部的（external）。在我使用它之前需要导入到文档中

   [C#]

   // First you need to clone the node template, and 

   // import it, because it originates from a different 

   // document

   System.Xml.XmlNode copy_node = new_node.Clone();

   System.Xml.XmlNode insert_node = 

      xml_document.ImportNode(copy_node, true);

   // Next locate which node should be its parent, and 

   // insert it

   string xpath_query = 

      buildXPathQuery(this.SelectedNode);

   System.Xml.XmlNode node = 

      xml_document.DocumentElement.SelectSingleNode(

      xpath_query);

   node.AppendChild(insert_node);

   // Finally, apply the xpath filter to determine what 

   // to display

   System.Xml.XmlNode expr = 

      insert_node.SelectSingleNode(xpath_filter);

   System.Windows.Forms.TreeNode new_child = 

      SelectedNode.Nodes.Add(expr.Value);

   populateTreeControl(insert_node, new_child.Nodes);

   // Select the node, to force the tree to expand

   SelectedNode = new_child;

   // And start editing the new folder name

   suppress_label_edit = false;

   new_child.BeginEdit();   

   [VB]

   ' First you need to clone the node template, and 

   ' import it, because it originates from a different 

   ' document.

   Dim copy_node As System.Xml.XmlNode = new_node.Clone()

   Dim insert_node As System.Xml.XmlNode = _

      xml_document.ImportNode(copy_node, True)

   ' Next locate which node should be its parent, 

   ' and insert it

   Dim xpath_query As String = _

      buildXPathQuery(Me.SelectedNode)

   Dim node As System.Xml.XmlNode = 

      xml_document.DocumentElement.SelectSingleNode( _

      xpath_query)

   node.AppendChild(insert_node)

   ' Finally, apply the xpath filter to determine what 

   ' should be

   ' displayed

   Dim expr As System.Xml.XmlNode = _

      insert_node.SelectSingleNode(xpath_filter)

   Dim new_child As System.Windows.Forms.TreeNode = _

      SelectedNode.Nodes.Add(expr.Value)

   populateTreeControl(insert_node, new_child.Nodes)

   ' Select the node, to force the tree to expand

   SelectedNode = new_child

   ' And start editing the new folder name

   suppress_label_edit = False

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