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

@NETscape, it doesn't work for me if I try to type `Key.Multiply` in TextBox when `Level 0` item is selected — ASh, Sep 02 '15 at 13:53
Ahh, now I made the item selectable, selected it first, and it didn't work. Interesting! — Kcvin, Sep 02 '15 at 13:56

score 16 · Accepted Answer · edited May 23 '17 at 11:45

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
                });
    }
}

score 5 · Answer 2 · answered Aug 28 '15 at 07:50

I can suggest a keydown event for the textboxes that you have.

<TextBox Margin="5" KeyDown="TextBox_KeyDown"
                     BorderThickness="1" BorderBrush="Black" />


 private void TextBox_KeyDown(object sender, KeyEventArgs e)
 {
    TextBox txt = sender as TextBox;
    if(e.Key == Key.Subtract)
    {
        txt.Text += "-";
        txt.SelectionStart = txt.Text.Length;
        txt.SelectionLength = 0;
        e.Handled = true;
    }
    else if (e.Key == Key.Multiply)
    {
        txt.Text += "*";
        txt.SelectionStart = txt.Text.Length;
        txt.SelectionLength = 0;
        e.Handled = true;
    }
}

It's not a good solution but it works. If you have any other "problem" keys, you can add an if to the event.

SelectionStart and SelectionLength are for positioning cursor at the end of textbox. And e.Handled = true; does prevent the default behaviour.

thank you for suggestion, `txt.Text += "-";` is not exactly what I needed (there can be selected text to replace). I had to find another workaround — ASh, Aug 28 '15 at 08:47

TreeViewItem with TextBox in WPF: type special characters

2 Answers2