TreeViewCancelEventArgs::Node Property

 

Gets the tree node to be checked, expanded, collapsed, or selected.

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

public:
property TreeNode^ Node {
	TreeNode^ get();
}

Property Value

Type: System.Windows.Forms::TreeNode^

The TreeNode to be checked, expanded, collapsed, or selected.

The following example demonstrates how to change the collapse state of a TreeView so that all the checked nodes are visible. First, all the nodes are collapsed, and a handler is added to the TreeView::BeforeExpand event. Next, all the nodes are expanded. The TreeView::BeforeExpand event handler determines whether a given node has child nodes that are checked. If a node does not have checked children, the expansion is canceled for that node. In order to allow normal node expansion when the plus sign next to a node is clicked, the TreeView::BeforeExpand event handler is then removed.

This behavior can also be implemented by handling the TreeView::BeforeCollapse event, as illustrated in the example for that topic.

For the complete example, see the TreeView::CheckBoxes reference topic.

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;
   }

.NET Framework
Available since 1.1
Return to top
Show: