TreeViewCancelEventArgs (Clase) (System.Windows.Forms)

Private Sub showCheckedNodesButton_Click(ByVal sender As Object, ByVal e As EventArgs)
    ' Disable redrawing of treeView1 to prevent flickering 
    ' while changes are made.
    treeView1.BeginUpdate()

    ' Collapse all nodes of treeView1.
    treeView1.CollapseAll()

    ' Add the CheckForCheckedChildren event handler to the BeforeExpand event.
    AddHandler treeView1.BeforeExpand, AddressOf CheckForCheckedChildren

    ' Expand all nodes of treeView1. Nodes without checked children are 
    ' prevented from expanding by the checkForCheckedChildren event handler.
    treeView1.ExpandAll()

    ' Remove the checkForCheckedChildren event handler from the BeforeExpand 
    ' event so manual node expansion will work correctly.
    RemoveHandler treeView1.BeforeExpand, AddressOf CheckForCheckedChildren

    ' Enable redrawing of treeView1.
    treeView1.EndUpdate()
End Sub 'showCheckedNodesButton_Click

' Prevent expansion of a node that does not have any checked child nodes.
Private Sub CheckForCheckedChildren(ByVal sender As Object, ByVal e As TreeViewCancelEventArgs)
    If Not HasCheckedChildNodes(e.Node) Then
        e.Cancel = True
    End If
End Sub 'CheckForCheckedChildren

' Returns a value indicating whether the specified 
' TreeNode has checked child nodes.
Private Function HasCheckedChildNodes(ByVal node As TreeNode) As Boolean
    If node.Nodes.Count = 0 Then
        Return False
    End If
    Dim childNode As TreeNode
    For Each childNode In node.Nodes
        If childNode.Checked Then
            Return True
        End If
        ' Recursively check the children of the current child node.
        If HasCheckedChildNodes(childNode) Then
            Return True
        End If
    Next childNode
    Return False
End Function 'HasCheckedChildNodes

private void showCheckedNodesButton_Click(object sender, EventArgs e)
{
    // Disable redrawing of treeView1 to prevent flickering 
    // while changes are made.
    treeView1.BeginUpdate();

    // Collapse all nodes of treeView1.
    treeView1.CollapseAll();

    // Add the checkForCheckedChildren event handler to the BeforeExpand event.
    treeView1.BeforeExpand += checkForCheckedChildren;

    // Expand all nodes of treeView1. Nodes without checked children are 
    // prevented from expanding by the checkForCheckedChildren event handler.
    treeView1.ExpandAll();

    // Remove the checkForCheckedChildren event handler from the BeforeExpand 
    // event so manual node expansion will work correctly.
    treeView1.BeforeExpand -= checkForCheckedChildren;

    // Enable redrawing of treeView1.
    treeView1.EndUpdate();
}

// Prevent expansion of a node that does not have any checked child nodes.
private void CheckForCheckedChildrenHandler(object sender, 
    TreeViewCancelEventArgs e)
{
    if (!HasCheckedChildNodes(e.Node)) e.Cancel = true;
}

// Returns a value indicating whether the specified 
// TreeNode has checked child nodes.
private bool HasCheckedChildNodes(TreeNode node)
{
    if (node.Nodes.Count == 0) return false;
    foreach (TreeNode childNode in node.Nodes)
    {
        if (childNode.Checked) return true;
        // Recursively check the children of the current child node.
        if (HasCheckedChildNodes(childNode)) return true;
    }
    return false;
}

private:
   void showCheckedNodesButton_Click( Object^ /*sender*/, EventArgs^ /*e*/ )
   {
      // Disable redrawing of treeView1 to prevent flickering 
      // while changes are made.
      treeView1->BeginUpdate();

      // Collapse all nodes of treeView1.
      treeView1->CollapseAll();

      // Add the checkForCheckedChildren event handler to the BeforeExpand event.
      treeView1->BeforeExpand += checkForCheckedChildren;

      // Expand all nodes of treeView1. Nodes without checked children are 
      // prevented from expanding by the checkForCheckedChildren event handler.
      treeView1->ExpandAll();

      // Remove the checkForCheckedChildren event handler from the BeforeExpand 
      // event so manual node expansion will work correctly.
      treeView1->BeforeExpand -= checkForCheckedChildren;

      // Enable redrawing of treeView1.
      treeView1->EndUpdate();
   }

   // Prevent expansion of a node that does not have any checked child nodes.
   void CheckForCheckedChildrenHandler( Object^ /*sender*/, TreeViewCancelEventArgs^ e )
   {
      if (  !HasCheckedChildNodes( e->Node ) )
            e->Cancel = true;
   }


   // Returns a value indicating whether the specified 
   // TreeNode has checked child nodes.
   bool HasCheckedChildNodes( TreeNode^ node )
   {
      if ( node->Nodes->Count == 0 )
            return false;

      System::Collections::IEnumerator^ myEnum = node->Nodes->GetEnumerator();
      while ( myEnum->MoveNext() )
      {
         TreeNode^ childNode = safe_cast<TreeNode^>(myEnum->Current);
         if ( childNode->Checked )
                  return true;

         // Recursively check the children of the current child node.
         if ( HasCheckedChildNodes( childNode ) )
                  return true;
      }

      return false;
   }

private void showCheckedNodesButton_Click(Object sender, EventArgs e)
{
    // Disable redrawing of treeView1 to prevent flickering 
    // while changes are made.
    treeView1.BeginUpdate();
    // Collapse all nodes of treeView1.
    treeView1.CollapseAll();
    // Add the checkForCheckedChildren event handler to the
    // BeforeExpand event.
    treeView1.add_BeforeExpand(checkForCheckedChildren);
    // Expand all nodes of treeView1. Nodes without checked children are 
    // prevented from expanding by the checkForCheckedChildren event handler.
    treeView1.ExpandAll();
    // Remove the checkForCheckedChildren event handler from
    // the BeforeExpand 
    // event so manual node expansion will work correctly.
    treeView1.remove_BeforeExpand(checkForCheckedChildren);
    // Enable redrawing of treeView1.
    treeView1.EndUpdate();
} //showCheckedNodesButton_Click

// Prevent expansion of a node that does not have any checked child nodes.
private void CheckForCheckedChildrenHandler(Object sender,
    TreeViewCancelEventArgs e)
{
    if (!(HasCheckedChildNodes(e.get_Node()))) {
        e.set_Cancel(true);
    }
} //CheckForCheckedChildrenHandler

// Returns a value indicating whether the specified 
// TreeNode has checked child nodes.
private boolean HasCheckedChildNodes(TreeNode node)
{
    if (node.get_Nodes().get_Count() == 0) {
        return false;
    }
    for (int iCtr = 0; iCtr < node.get_Nodes().get_Count(); iCtr++) {
        TreeNode childNode = node.get_Nodes().get_Item(iCtr);
        if (childNode.get_Checked()) {
            return true;
        }
        // Recursively check the children of the current child node.
        if (HasCheckedChildNodes(childNode)) {
            return true;
        }
    }
    return false;
} //HasCheckedChildNodes