title: Error between classes
body: <p>To explain my problem I made this code.</p>
  
  <p>The application will run the class <code>control</code> and from there it will create the new instances of the two other classes <code>serial</code> and <code>UIcontrol</code>.</p>
  
  <p>In <code>UI control</code> a function will call a function in <code>control</code> which will call a function in <code>serial</code> which will call a function in <code>control</code> which will call a function in <code>UIcontrol</code> which will do something else.</p>
  
  <p>I know this is insane but I need this functionality.</p>
  
  <pre><code>public class control // My application will enter here
  {
      private serial serial_;
      private UIcontrol UIcontrol_;
  
      public control()
      {
          serial_ = new serial(this);
          UIcontrol_ = new UIcontrol(this);
      }
  
      public void controlToGUI()
      {
          UIcontrol_.stopHere();
      }
  
      public void controlToSerial()
      {
          serial_.serialToControl();
      }
  }
  
  public class UIcontrol
  {
      private static control myParent;
  
      public UIcontrol(control parent)
      {
          myParent = parent;
          UItoControl();
      }
  
      public void UItoControl()
      {
          myParent.controlToSerial();
      }
  
      public void stopHere()
      {
          int i = 2;
      }
  }
  
  public class serial
  {
      private static control myParent;
  
      public serial(control parent)
      {
          myParent = parent;
      }
  
      public void serialToControl()
      {
          myParent.controlToGUI();
      }
  }
  </code></pre>
  
  <p>I get the error <code>An unhandled exception of type 'System.NullReferenceException' occurred in Test App.exe</code> when the code reach:</p>
  
  <pre><code>    public void controlToGUI()
      {
          UIcontrol_.stopHere(); // This line gives me the error
      }
  </code></pre>