TreeView.TopNode Proprietà

Definizione

Spazio dei nomi:

System.Windows.Forms

Assembly:

System.Windows.Forms.dll

Ottiene o imposta il primo nodo dell'albero completamente visibile nel controllo di visualizzazione albero.

public:
 property System::Windows::Forms::TreeNode ^ TopNode { System::Windows::Forms::TreeNode ^ get(); void set(System::Windows::Forms::TreeNode ^ value); };

[System.ComponentModel.Browsable(false)]
public System.Windows.Forms.TreeNode TopNode { get; set; }

[<System.ComponentModel.Browsable(false)>]
member this.TopNode : System.Windows.Forms.TreeNode with get, set

Public Property TopNode As TreeNode

Valore della proprietà

TreeNode

Oggetto TreeNode che rappresenta il primo nodo della struttura ad albero completamente visibile nel controllo di visualizzazione ad albero.

Attributi

BrowsableAttribute

Esempio

Nell'esempio di codice seguente viene illustrato come usare i BeforeLabelEditAfterSelect membri e TopNode . Per eseguire questo esempio, incollare il codice seguente in una maschera contenente un TreeView controllo denominato TreeView1. Chiamare il InitializeTreeView metodo nel costruttore o Load nel metodo del form.

private:
   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" );
      }

   }

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 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");
    }
}

Private Sub InitializeTreeView()

    ' Construct the TreeView object.
    Me.TreeView1 = New System.Windows.Forms.TreeView

    ' Set dock, location, size name, and tab order
    ' values for the TreeView object.

    With TreeView1
        .Dock = System.Windows.Forms.DockStyle.Left
        .Location = New System.Drawing.Point(0, 0)
        .Name = "TreeView1"
        .Size = New System.Drawing.Size(152, 266)
        .TabIndex = 1
    End With

    ' Set the LabelEdit property to true to allow the 
    ' user to edit the TreeNode text.
    Me.TreeView1.LabelEdit = True

    ' Declare and create objects needed to populate 
    ' the TreeView.
    Dim file, files(), filePath As String
    files = New String() {"bigPresentation.ppt", "myFinances.xls", _
        "myResume.doc"}
    filePath = "c:\myFiles"
    Dim nodes As 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 Each file In files
        Dim node As New TreeNode(file)
        node.Tag = filePath & "\" & file
        nodes.Add(node)
    Next

    ' Create a new node named topNode and add the ArrayList of 
    ' nodes to topNode.
    Dim topNode As New TreeNode("myFiles", _
        nodes.ToArray(GetType(TreeNode)))

    topNode.Tag = filePath

    ' Add topNode to the TreeView.
    TreeView1.Nodes.Add(topNode)

    ' Add the TreeView to the form.
    Me.Controls.Add(TreeView1)
End Sub

Private Sub TreeView1_BeforeLabelEdit(ByVal sender As Object, _
    ByVal e As NodeLabelEditEventArgs) Handles TreeView1.BeforeLabelEdit

    ' Determine whether the user has selected the top node. If so,
    ' change the CancelEdit property to true to cancel the edit.  
    If (e.Node Is TreeView1.TopNode) Then

        e.CancelEdit = True
        MessageBox.Show("You are not allowed to edit the top node")
    End If


End Sub

private:
   // 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!" );
            break;

         case TreeViewAction::ByMouse:
            MessageBox::Show( "You like the mouse!" );
            break;
      }
   }

// 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;
    }
}

' Handle the After_Select event.
Private Sub TreeView1_AfterSelect(ByVal sender As System.Object, _
    ByVal e As System.Windows.Forms.TreeViewEventArgs) _
        Handles TreeView1.AfterSelect

    ' Vary the response depending on which TreeViewAction
    ' triggered the event. 
    Select Case (e.Action)
        Case TreeViewAction.ByKeyboard
            MessageBox.Show("You like the keyboard!")
        Case TreeViewAction.ByMouse
            MessageBox.Show("You like the mouse!")
    End Select
End Sub

Commenti

Inizialmente, restituisce TopNode il primo nodo della struttura ad albero radice, che si trova nella parte superiore di TreeView. Tuttavia, se l'utente ha eseguito lo scorrimento del contenuto, un altro nodo della struttura ad albero potrebbe trovarsi nella parte superiore.

Nota

L'impostazione di questa proprietà non ha alcun effetto quando il valore della Scrollable proprietà è false.

Vedi anche

• IsVisible