title: Raise event when string changed
body: <p>I need to create some interface to read data from iButton. Actually it work's like that: user applies little pendant with magnet to iButton device -> log in him. User take away pendant - logout.</p>
  
  <p>My problem is that, I know how to relog, by simple:</p>
  
  <pre><code> public static void sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
          {
              if (sp.ReadLine() == "logout")
              {
                 logoutUser();
              }
              else 
              {
                  //put data into nonstatic textbox from another window
                 // or raise some event which will listen to changes in data and put string into textbox
              }
          }
  </code></pre>
  
  <p>But how can I raise event when data != "logout" (for example A0019293881, as pin code).</p>