I have no idea what your code looks like, anyway even I was stuck once while doing backspace. Here is a sample example of a code to allow only numeric values-
protected override void OnKeyDown(KeyEventArgs e)
{
if (char.IsNumber((char)e.KeyValue) || (((char)e.KeyData) == '\b'))
{
e.SuppressKeyPress = false;
}
else { e.SuppressKeyPress = true; }
}
Have a look at the second part of the If condition -
((char)e.KeyData) == '\b')
This will allow you to use backspace in your textbox.
Hope this helps.
I have created one such control explained in my blog here -
http://tarundotnet.wordpress.com/2011/06/26/allow-numbers-or-letters-and-disable-right-click-in-textbox/[
^]