Custom Numeric TextBox

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)
{
    //To only allow numbers
    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/[^]