WPF TreeView, get TreeViewItem in PreviewMouseDown event - wpf

Question

How can I determine TreeViewItem clicked in PreviewMouseDown event?

Answer 1

The following seems to work:
private void myTreeView_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
TreeViewItem item = GetTreeViewItemClicked((FrameworkElement)e.OriginalSource,
myTreeView);
...
}
private TreeViewItem GetTreeViewItemClicked(FrameworkElement sender, TreeView treeView)
{
Point p = ((sender as FrameworkElement)).TranslatePoint(new Point(0, 0), treeView);
DependencyObject obj = treeView.InputHitTest(p) as DependencyObject;
while (obj != null && !(obj is TreeViewItem))
obj = VisualTreeHelper.GetParent(obj);
return obj as TreeViewItem;
}

Answer 2

I originally used an extension method on TreeView that takes a UIElement--the sender of the PreviewMouseDown event--like this:
private void MyTreeView_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
var uiElement = sender as UIElement;
var treeViewItem = myTreeView.TreeViewItemFromChild(uiElement);
}
Here's the extension method (it checks the child itself in case you clicked right on a TreeViewItem directly)...
public static TreeViewItem TreeViewItemFromChild(this TreeView treeView, UIElement child)
{
UIElement proposedElement = child;
while ((proposedElement != null) && !(proposedElement is TreeViewItem))
proposedElement = VisualTreeHelper.GetParent(proposedElement) as UIElement;
return proposedElement as TreeViewItem;
}
Update:
However, I've since switched it to a more generic version that I can use anywhere.
public static TAncestor FindAncestor<TAncestor>(this UIElement uiElement)
{
while ((uiElement != null) && !(uiElement is TAncestor))
retVal = VisualTreeHelper.GetParent(uiElement) as UIElement;
return uiElement as TAncestor;
}
That either finds the type you're looking for (again, including checking itself) or returns null
You'd use it in the same PreviewMouseDown handler like so...
private void MyTreeView_PreviewMouseDown(object sender, MouseButtonEventArgs e)
{
var uiElement = sender as UIElement;
var treeViewItem = uiElement.FindAncestor<TreeViewItem>();
}
This came in very handy for when my TreeViewItem had a CheckBox in its template and I wanted to select the item when the user clicked the checkbox which normally swallows the event.
Hope this helps!