Question

I have a handle for a currency value. It should allow negative value say -555.

On keydown/Keypress, when I try to find the Key value for Subtract key in Numpad, it gives me as Key.Subtract in IE versions. But in chrome/firefox latest versions, it shows me as Key.Unknown.

Is there any specific handle needs to be done.

Sample:

if ((e.Key >= Key.D0 && e.Key <= Key.D9) || (e.Key >= Key.NumPad0 && e.Key <= Key.NumPad9) || (e.Key == Key.Subtract) || (e.Key == Key.Unknown))
            {
                //valid number, but if shift is pressed, it is an invalied character
                if (Keyboard.Modifiers == ModifierKeys.Shift)
                    e.Handled = true;
            }            
            else
                e.Handled = true;

Here, I have handled the unknown key explicitly. But is there any standard way to get rid of this? Please help me.

Answer 1

I have run into the same problem when some customers do not use IE. What you have to do is you have to check the value of PlatformKeyCode which has difference value on difference OS, for example, PlatformKeyCode of . is 190 on a Windows but it is 47 on Mac.

Below statement quoted from KeyEventArgs.PlatformKeyCode Property on MSDN.

The portable key codes are a common subset of all the possible key
codes of the supported operating systems, in this case, Macintosh and
Windows. For example, the keystroke ‘v’ is represented as a Key value
(which would evaluate as 51 if you cast it to an integer, but is more
useful if you retain the enumeration information). That key would have
a PlatformKeyCode value of 86. Certain keystrokes, however, are not
portable, such as the SCROLL LOCK key for Microsoft Windows. In this
case, the Key value is Unknown, which is the value for any nonportable
key, and the PlatformKeyCode is 145 on a Windows platform. For
information about Microsoft Windows-specific key codes, see
“Virtual-Key Codes” in the MSDN Library. For information on
Macintosh-specific key codes, see Keyboard Layout Services Reference
on the Apple Developer Connection Web site.

On my machine the PlatformKeyCode value of - is 189.