TreeViewItem with TextBox in WPF: type special characters

Question

I need to edit some hierarchical structure and I use TreeView with TextBoxes

Short example

<TreeView>
    <TreeView.Items>
        <TreeViewItem Header="Level 0">
            <!-- Level 1-->
            <TextBox Margin="5"
                     BorderThickness="1" BorderBrush="Black" />
        </TreeViewItem>
    </TreeView.Items>
</TreeView>

When I type in TextBox, +, -, letters and digits work fine, arrows work but when I press -, Level 0 item collapses and when I type *, nothing happens

How should I handle - and * to see them in TextBox as expected?

Edit:

- works if typed as Key.OemMinus but not from numeric keyboard as Key.Subtract

* works if typed as Shift+Key.D8 but not from numeric keyboard as Key.Multiply

Answer 1

finally solved the problem with Key.Subtract

I added handler to PreviewKeyDown on TextBox

<TextBox Margin="5" BorderThickness="1" BorderBrush="Black" 
         PreviewKeyDown="TextBoxPreviewKeyDown"
/>

on receiving Key.Subtract, KeyDown is marked as handled and then i manually raise TextInput event as explained in this answer (How can I programmatically generate keypress events in C#? )

private void TextBoxPreviewKeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Subtract)
    {
        e.Handled = true;

        var text = "-";
        var target = Keyboard.FocusedElement;
        var routedEvent = TextCompositionManager.TextInputEvent;

        target.RaiseEvent(
            new TextCompositionEventArgs
                (
                     InputManager.Current.PrimaryKeyboardDevice,
                    new TextComposition(InputManager.Current, target, text)
                )
                {
                    RoutedEvent = routedEvent
                });
    }
}