Silverlight NumericUpDown: Set max character length, or validate against it? - silverlight

Question

I'm attempting to use the key up event to hijack the event and prevent two things. Anything but numeric keys or delete/back as well as once they hit a certain max of character length, inhibit the entry.
This solves the first validation portion, but I can't seem to figure out a way to prevent entry past a certain character length.
private void numericFieldInputField_KeyUp(object sender, KeyEventArgs e)
{
if (e.Key == Key.D0 || e.Key == Key.D1 || e.Key == Key.D2 || e.Key == Key.D3 || e.Key == Key.D4 || e.Key == Key.D5 ||
e.Key == Key.D6 || e.Key == Key.D7 || e.Key == Key.D8 || e.Key == Key.D9 || e.Key == Key.NumPad0 || e.Key == Key.NumPad1 ||
e.Key == Key.NumPad2 || e.Key == Key.NumPad3 || e.Key == Key.NumPad4 || e.Key == Key.NumPad5 || e.Key == Key.NumPad6 ||
e.Key == Key.NumPad7 || e.Key == Key.NumPad8 || e.Key == Key.NumPad9 || e.Key == Key.Back || e.Key == Key.Delete ||
e.Key == Key.Left || e.Key == Key.Right || e.Key == Key.Up || e.Key == Key.Down || e.Key == Key.Tab)
{
e.Handled = true;
}
else
{
//show validation
}
}
When I check the length of the numeric updown's value, cast it to string and look at the length property at this point, the last character they entered won't register. Also, when I set e.Handled to true, it still enters the character into the input. I thought e.Handled = true would keep the UI from putting the character into the input?

Answer 1

I would suggest using a Validator. In the databinding you specify the validator you want, the framework takes care of the rest. Here's one good intro to the topic: Tutorial