TdxTreeViewNodeAllowEvent Type

The action permission procedural type for tree nodes.

Declaration

delphi

TdxTreeViewNodeAllowEvent = procedure(Sender: TdxCustomTreeView; ANode: TdxTreeViewNode; var Allow: Boolean) of object;

Parameters

Name	Type	Description
Sender	TdxCustomTreeView

The Tree View control that raised an action permission event.

| | ANode | TdxTreeViewNode |

The target tree node.

| | Allow | Boolean |

Assign False to this parameter to prohibit users from performing the action. To allow the action, assign False to the parameter.

Remarks

The OnCollapsing event handler below prohibits the control from collapsing nodes at the top nesting level:

Delphi
C++

delphi

procedure TForm1.dxTreeViewControl1Collapsing(Sender: TdxCustomTreeView;
  ANode: TdxTreeViewNode; var Allow: Boolean);
begin
  if ANode.Parent = Sender.Root then
    Allow := False;
end;

cpp

void __fastcall TForm1::dxTreeViewControl1Collapsing(TdxCustomTreeView *Sender,
  TdxTreeViewNode *ANode, bool &Allow)
{
  if (ANode->Parent == Sender->Root)
    Allow = false;
}

The following Tree View events reference the TdxTreeViewNodeAllowEvent type: