C#

<br />
private void myHexTextbox_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)<br />
{<br />
    string Allowed = @"0123456789ABCDEFabcdef";     // all the hex characters<br />
    if (Allowed.IndexOf(e.KeyChar)==-1)<br />
    {<br />
        e.Handled = true;	// By setting this as handled the character will be ignored				<br />
    }<br />
}<br />

#if DEBUG
// logging code here
#endif

α.γεεκ

Fortune passes everywhere.
Duke Leto Atreides

class Log
{
  private static bool m_enabled = System.Configuration.ConfigurationSettings.AppSettings["Logging"] == "true";
 
  public static bool Enabled
  {
     get { return m_enabled; }
  }
 
  public static void Error(string message)
  {
     if (Enabled)
        // do the logging here
  }
 
  public static void Info(string message)
  ....
}

private void ListeningThread(void)<br />
{<br />
     TcpListener oListener = new TcpListener();<br />
  <br />
     _mnThreadCount ++;<br />
<br />
     oListener.Listen(nWhateverPortYouWant)<br />
     while(!_mbCloseThreads)<br />
     {<br />
       // .. do the work here<br />
     }<br />
<br />
     _mnThreadCount -- ;<br />
}

public override OnStart()<br />
{<br />
    _mbCloseThreads = false;<br />
    _mnThreadCount = 0;<br />
<br />
    ThreadStart oThreadStart = new ThreadStart((void)this.ListeningThread);<br />
    Thread oThread = new Thread(oThreadStart);<br />
<br />
    oThread.Start();<br />
}

public override OnStop()<br />
{<br />
    _mbCloseThreads = true;<br />
    while(_mnThreadCount > 0)<br />
        Thread.Sleep(1);<br />
}