title: Numpad0 not working with char.IsLetterOrDigit
body: <p>I have a method that I call when a the KeyUp event fires on my control and within that method I check the key pressed is a letter or digit using the char.IsLetterOrDigit method. However it doesn't seem to work with the KeyPad numbers!?</p>
  
  <p>My code is below:</p>
  
  <pre><code>    void MyControls_KeyUp(object sender, KeyEventArgs e)
      {
          if ((char.IsLetterOrDigit(Convert.ToChar(e.KeyValue))))
          {
              ....
          }
      }
  </code></pre>
  
  <p>Anybody any ideas why this doesn't work?</p>
  
  <p>Thanks in advance.</p>
  
  <p>I'm using C#4.0</p>