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TreeView.BeforeLabelEdit-Ereignis

Tritt ein, bevor der Text der Strukturknotenbezeichnung bearbeitet wird.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

public event NodeLabelEditEventHandler BeforeLabelEdit
/** @event */
public void add_BeforeLabelEdit (NodeLabelEditEventHandler value)

/** @event */
public void remove_BeforeLabelEdit (NodeLabelEditEventHandler value)

JScript unterstützt die Verwendung von Ereignissen, aber nicht die Deklaration von neuen Ereignissen.

Weitere Informationen zum Behandeln von Ereignissen finden Sie unter Behandeln von Ereignissen.

Im folgenden Codebeispiel wird die Verwendung der Member BeforeLabelEdit, AfterSelect und TopNode veranschaulicht. Fügen Sie zum Ausführen dieses Beispiels den folgenden Code in ein Formular ein, das ein TreeView-Steuerelement mit dem Namen TreeView1 enthält. Rufen Sie die InitializeTreeView-Methode im Konstruktor oder in der Load-Methode des Formulars auf.

	private void InitializeTreeView()
	{

		// Construct the TreeView object.
		this.TreeView1 = new System.Windows.Forms.TreeView();

		// Set dock, location, size name, and tab order
		// values for the TreeView object.
		TreeView1.Dock = System.Windows.Forms.DockStyle.Left;
		TreeView1.Location = new System.Drawing.Point(0, 0);
		TreeView1.Name = "TreeView1";
		TreeView1.Size = new System.Drawing.Size(152, 266);
		TreeView1.TabIndex = 1;
		
		// Associate the event-handling methods with the
		// BeforeLabeEdit and the AfterSelect events.
		TreeView1.BeforeLabelEdit += 
			new NodeLabelEditEventHandler(TreeView1_BeforeLabelEdit);
		TreeView1.AfterSelect += 
			new TreeViewEventHandler(TreeView1_AfterSelect);

		// Set the LabelEdit property to true to allow the 
		// user to edit the TreeNode text.
		this.TreeView1.LabelEdit = true;

		// Declare and create objects needed to populate 
		// the TreeView.
		string[] files = new string[]{"bigPresentation.ppt", 
			"myFinances.xls", "myResume.doc"};; 
		string filePath = "c:\\myFiles";
		System.Collections.ArrayList nodes = 
			new System.Collections.ArrayList();

		// Create a node for each file, setting the Text property to the 
		// file's name and the Tag property to file's fully-qualified name.
		foreach ( string file in files )
		{
			TreeNode node = new TreeNode(file);
			node.Tag = filePath+"\\"+file;
			nodes.Add(node);
		}

		TreeNode[] treeNodes = new TreeNode[nodes.Count];
		nodes.CopyTo(treeNodes);

		// Create a new node named topNode and add the ArrayList of 
		// nodes to topNode.
		TreeNode topNode = new TreeNode("myFiles",  treeNodes);
		topNode.Tag = filePath;

		// Add topNode to the TreeView.
		TreeView1.Nodes.Add(topNode);

		// Add the TreeView to the form.
		this.Controls.Add(TreeView1);
	}

	private void TreeView1_BeforeLabelEdit(object sender, 
		NodeLabelEditEventArgs e)
	{

		// Determine whether the user has selected the top node. If so,
		// change the LabelEdit property to false so the user cannot
		// edit this label.  
		if (e.Node == TreeView1.TopNode)

		{
			TreeView1.LabelEdit = false;
			MessageBox.Show("You are not allowed to edit the top node");
		}
		// Set the LabelEdit property to true again.
		TreeView1.LabelEdit = true;
	}
...	// Handle the After_Select event.
	private void TreeView1_AfterSelect(System.Object sender, 
		System.Windows.Forms.TreeViewEventArgs e)
	{

		// Vary the response depending on which TreeViewAction
		// triggered the event. 
		switch((e.Action))
		{
			case TreeViewAction.ByKeyboard:
				MessageBox.Show("You like the keyboard!");
				break;
			case TreeViewAction.ByMouse:
				MessageBox.Show("You like the mouse!");
				break;
		}
	}

    private void InitializeTreeView()
    {
        // Construct the TreeView object.
        this.treeView1 = new System.Windows.Forms.TreeView();
        // Set dock, location, size name, and tab order
        // values for the TreeView object.
        treeView1.set_Dock(System.Windows.Forms.DockStyle.Left);
        treeView1.set_Location(new System.Drawing.Point(0, 0));
        treeView1.set_Name("TreeView1");
        treeView1.set_Size(new System.Drawing.Size(152, 266));
        treeView1.set_TabIndex(1);
        // Associate the event-handling methods with the
        // BeforeLabeEdit and the AfterSelect events.
        treeView1.add_BeforeLabelEdit(
            new NodeLabelEditEventHandler(treeView1_BeforeLabelEdit));
        treeView1.add_AfterSelect(new TreeViewEventHandler(
            treeView1_AfterSelect));
        // Set the LabelEdit property to true to allow the 
        // user to edit the TreeNode text.
        this.treeView1.set_LabelEdit(true);
        // Declare and create objects needed to populate 
        // the TreeView.
        String files[] = new String[] { "bigPresentation.ppt", "myFinances.xls",
            "myResume.doc" };
        String filePath = "c:\\myFiles";
        System.Collections.ArrayList nodes = new System.Collections.ArrayList();
        // Create a node for each file, setting the Text property to the 
        // file's name and the Tag property to file's fully-qualified name.
        for (int iCtr = 0; iCtr < files.length; iCtr++) {
            String file = files[iCtr];
            TreeNode node = new TreeNode(file);
            node.set_Tag(filePath + "\\" + file);
            nodes.Add(node);
        }

        TreeNode treeNodes[] = new TreeNode[nodes.get_Count()];
        nodes.CopyTo(treeNodes);
        // Create a new node named topNode and add the ArrayList of 
        // nodes to topNode.
        TreeNode topNode = new TreeNode("myFiles", treeNodes);
        topNode.set_Tag(filePath);
        // Add topNode to the TreeView.
        treeView1.get_Nodes().Add(topNode);
        // Add the TreeView to the form.
        this.get_Controls().Add(treeView1);
    } //InitializeTreeView

    private void treeView1_BeforeLabelEdit(Object sender,
        NodeLabelEditEventArgs e)
    {
        // Determine whether the user has selected the top node. If so,
        // change the LabelEdit property to false so the user cannot
        // edit this label.  
        if (e.get_Node().Equals(treeView1.get_TopNode())) {
            treeView1.set_LabelEdit(false);
            MessageBox.Show("You are not allowed to edit the top node");
        }
        // Set the LabelEdit property to true again.
        treeView1.set_LabelEdit(true);
    } //treeView1_BeforeLabelEdit
...    // Handle the After_Select event.
    private void treeView1_AfterSelect(Object sender,
        System.Windows.Forms.TreeViewEventArgs e)
    {
        // Vary the response depending on which TreeViewAction
        // triggered the event. 
        switch (e.get_Action()) {
            case TreeViewAction.ByKeyboard:
                MessageBox.Show("You like the keyboard!");
                break;
            case TreeViewAction.ByMouse:
                MessageBox.Show("You like the mouse!");
                break;
        }
    } //treeView1_AfterSelect

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