How to Only allow numbers and a Minus "-" in a Textbox

Question

I would like to know how I would be able to allow only numbers and a "-" minus sign in a textbox?

Here is coding that I can already allow only numbers:

private void txtDicountSettlement_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
    Regex regex = new Regex("[^0-9]+");
    e.Handled = regex.IsMatch(e.Text);
}

Answer 1

Just add the - to your regex character group, in a position that's not making a range of characters:

private void txtDicountSettlement_PreviewTextInput(object sender, TextCompositionEventArgs e)
{
    Regex regex = new Regex("[^0-9-]+");
    e.Handled = regex.IsMatch(e.Text);
}