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Evento TreeView.BeforeLabelEdit

Aggiornamento: novembre 2007

Si verifica prima di aver modificato il testo dell'etichetta del nodo.

Spazio dei nomi:  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 non supporta gli eventi.

Per ulteriori informazioni sulla gestione di eventi, vedere Utilizzo degli eventi.

Nell'esempio di codice riportato di seguito viene illustrato come utilizzare i membri BeforeLabelEditAfterSelect e TopNode. Per eseguire l'esempio, incollare il codice riportato di seguito in un form contenente un controllo TreeView denominato TreeView1. Chiamare il metodo InitializeTreeView nel costruttore del form o nel metodo Load.

	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


Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition , Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

.NET Framework e .NET Compact Framework non supportano tutte le versioni di ciascuna piattaforma. Per un elenco delle versioni supportate, vedere Requisiti di sistema di .NET Framework.

.NET Framework

Supportato in: 3.5, 3.0, 2.0, 1.1, 1.0
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