Making selectable again a WPF TreeviewITem after the first click

Question

Hi, I have a TreeVIew WPF with 2 Levels of Data. I have deleted the ToogleButton from the TreeViewItemTemplate. Now I'd like to expand / collapse the groups with a single mouse-click (not with a double click as the default behaviour). I have tried in this way:

Private Sub tvArt_SelectedItemChanged(ByVal sender As System.Object, _ ByVal e As RoutedPropertyChangedEventArgs(Of System.Object)) Handles tvArt.SelectedItemChanged

If e.NewValue Is Nothing = False Then
    Dim ri As P_RicambiItem = TryCast(e.NewValue, P_RicambiItem)
    If ri Is Nothing = False Then
        If ri.isExpanded Then
            ri.isExpanded = False
        Else
            ri.isExpanded = True
        End If
        ri.isSelected = False
    End If
End If

End Sub

Using my properties "isExpanded" and "isSelected" in the collection data source. But it works only halfway: after the first click, infact, I can't click for a second time on the same item, because, even if I've deselected it, the event handler "remembers" that it was the last selected item and it doesn't capture the event "SelectedItemChanged". How can I do? Thanks a lot, Pileggi

Answer 1

Easiest way is probably to handle the PreviewMouseDown event on the TreeView and identify when the mouse clicks the parent TreeViewItems:

XAML:

<TreeView Name="treeView1" TreeView.PreviewMouseDown="OnTreeViewPreviewMouseDown" />

Code-behind:

private void OnTreeViewPreviewMouseDown( object sender, MouseButtonEventArgs e )
{
    TreeViewItem tvi = GetTreeViewItemClicked( (FrameworkElement) e.OriginalSource, treeView1 );
    if ( null == tvi ) return;
    tvi.IsExpanded = !tvi.IsExpanded;
}

private static TreeViewItem GetTreeViewItemClicked( UIElement sender, UIElement treeView )
{
    Point p = sender.TranslatePoint( new Point( 0, 0 ), treeView );
    var obj = treeView.InputHitTest( p ) as DependencyObject;
    while ( obj != null && !( obj is TreeViewItem ) )
    {
        obj = VisualTreeHelper.GetParent( obj );
    }
    return obj as TreeViewItem;
}

Answer 2

Thank you very much! It works very well, if someone should be interested, this is my Vb version:

Private Sub tvArt_PreviewMouseDown(ByVal sender As Object, ByVal e As MouseButtonEventArgs) Handles tvArt.PreviewMouseDown
    Dim tvi As TreeViewItem = GetTreeViewItemClicked(e.OriginalSource, Me.tvArt)
    If tvi Is Nothing = False Then
        If tvi.HasItems Then
            tvi.isExpanded = Not tvi.isExpanded
        End If
    End If
End Sub

Private Function GetTreeViewItemClicked(ByVal sender As UIElement, ByVal _treeView As UIElement) As TreeViewItem
    Dim p As Point = sender.TranslatePoint(New Point(0, 0), _treeView)
    Dim obj As DependencyObject = DirectCast(_treeView.InputHitTest(p), DependencyObject)
    While obj Is Nothing = False AndAlso TypeOf obj Is TreeViewItem = False
        obj = VisualTreeHelper.GetParent(obj)
    End While
    Return DirectCast(obj, TreeViewItem)
End Function