Question

In my TreeView, I have different events for MouseDown/MouseUp, etc but when I do it fast enough the TreeView expands/collapses the TreeNode. I don’t want this baked-in behaviour.

Is there a way to disable this?

Answer 1

You could suppress the double click event of TreeViewItem like so:

xaml:

<TreeView DockPanel.Dock="Left" TreeViewItem.PreviewMouseDoubleClick="TreeViewItem_PreviewMouseDoubleClick">
    <TreeViewItem Header="Node Level 1" IsExpanded="True" >
        <TreeViewItem Header="Node Level 2.1" >
            <TreeViewItem Header="MyItem" />
        </TreeViewItem>
        <TreeViewItem Header="Node Level 2.2">
            <TreeViewItem Header="MyItem" />
        </TreeViewItem>
    </TreeViewItem>
</TreeView>

code:

private void TreeViewItem_PreviewMouseDoubleClick(object sender, MouseButtonEventArgs e)
{
    //this will suppress the event that is causing the nodes to expand/contract 
    e.Handled = true;
}

UPDATE

According to msdn docs:

Although this routed event seems to
follow a tunneling route through an
element tree, it actually is a direct
routed event that is raised along the
element tree by each UIElement…
Control authors who want to handle
mouse double clicks should use the
PreviewMouseLeftButtonDown event when
ClickCount is equal to two. This will
cause the state of Handled to
propagate appropriately in the case
where another element in the element
tree handles the event.

I’m not sure if this why you are having issues or not, but we’ll do it the MSDN way and use PreviewMouseLeftButtonDown instead:

xaml:

<TreeView DockPanel.Dock="Left" TreeViewItem.PreviewMouseLeftButtonDown="TreeView_PreviewMouseLeftButtonDown">
    <TreeViewItem Header="Node Level 1" IsExpanded="True">
        <TreeViewItem Header="Node Level 2.1" >
            <TreeViewItem Header="MyItem" />
        </TreeViewItem>
        <TreeViewItem Header="Node Level 2.2">
            <TreeViewItem Header="MyItem" />
        </TreeViewItem>
    </TreeViewItem>
</TreeView>

code:

private void TreeView_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    if (e.ClickCount > 1)
    {
        //here you would probably want to include code that is called by your
        //mouse down event handler.
        e.Handled = true;
    }
}

I’ve tested this and it works no matter how many times i click