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BeforeLabelEdit Event

TreeView::BeforeLabelEdit Event

Occurs before the tree node label text is edited.

Namespace:  System.Windows.Forms
Assembly:  System.Windows.Forms (in System.Windows.Forms.dll)

 event NodeLabelEditEventHandler^ BeforeLabelEdit {
	void add (NodeLabelEditEventHandler^ value);
	void remove (NodeLabelEditEventHandler^ value);

For more information about how to handle events, see Handling and Raising Events.

The following code example demonstrates how to use the BeforeLabelEdit AfterSelect and TopNode members. To run this example, paste the following code in a form that contains a TreeView control that is named TreeView1. Call the InitializeTreeView method in the form's constructor or Load method.

   void InitializeTreeView()

      // Construct the TreeView object. 
      this->TreeView1 = gcnew 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 = System::Drawing::Point( 0, 0 );
      TreeView1->Name = "TreeView1";
      TreeView1->Size = System::Drawing::Size( 152, 266 );
      TreeView1->TabIndex = 1;

      // Associate the event-handling methods with the 
      // BeforeLabeEdit and the AfterSelect events.
      TreeView1->BeforeLabelEdit += gcnew NodeLabelEditEventHandler( this, &Form1::TreeView1_BeforeLabelEdit );
      TreeView1->AfterSelect += gcnew TreeViewEventHandler( this, &Form1::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. 
      array<String^>^files = {"bigPresentation.ppt","myFinances.xls","myResume.doc"};
      String^ filePath = "c:\\myFiles";
      System::Collections::ArrayList^ nodes = gcnew 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.
      System::Collections::IEnumerator^ myEnum = files->GetEnumerator();
      while ( myEnum->MoveNext() )
         String^ file = safe_cast<String^>(myEnum->Current);
         TreeNode^ node = gcnew TreeNode( file );
         node->Tag = String::Concat( filePath, "\\", file );
         nodes->Add( node );

      array<TreeNode^>^treeNodes = gcnew array<TreeNode^>(nodes->Count);
      nodes->CopyTo( treeNodes );

      // Create a new node named topNode and add the ArrayList of  
      // nodes to topNode.
      TreeNode^ topNode = gcnew 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 );

   void TreeView1_BeforeLabelEdit( Object^ /*sender*/, NodeLabelEditEventArgs^ e )

      // Determine whether the user has selected the top node. If so, 
      // change the CancelEdit property to true to cancel the edit. 
      if ( e->Node == TreeView1->TopNode )
         e->CancelEdit = true;
         MessageBox::Show( "You are not allowed to edit the top node" );



   // Handle the After_Select event. 
   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!" );

         case TreeViewAction::ByMouse:
            MessageBox::Show( "You like the mouse!" );
		The following method shows the use of the LabelEdit property.
		Add this method to a form containing a ListBox control named ListBox1.

		Call the method in the constructor or Load method of the form.


		The following class inherits from the Button class and overrides
		the OnMouseHover and OnMouseMove methods to give the button
		some special behavior. To use this example create a new form and copy paste this class in the same file, after the form class.  Add a button of
		type FunButton, defined in the code example, to the form. 

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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