Question

I’m trying to write a page that filters a ListBox depending on the contents of the textbox. I’ve got all the other stuff working but I want the ListBox to apply the filter with every KeyDown event that occurs in the TextBox. The problem is, when I capture the KeyDown event and then try to look at the TextBox.Text property, it remains empty. I imagine that this is due to the fact that the TextBox may only update the Text property when it loses focus.

Any thoughts on how I can get the current text in a TextBox during the KeyDown event without having to capture and rebuild the character array during each KeyDown?

Thanks!

Answer 1

Manual:

For keyboard input, WPF first sends the appropriate KeyDown/KeyUp events. If those events are not handled and the key is textual (rather than a control key such as directional arrows or function keys), then a TextInput event is raised.

In the KeyDown event, you can capture the key that’s pressed:

private void OnKeyDownHandler(object sender, KeyEventArgs e)
{
    Console.WriteLine(e.Key);
}

After the event exits, the pressed key is added to the .Text property, so the next time the KeyDown event is raised, you can read the previously entered characters from .Text.