title: switching between uiviewcontrollers without a UI navigator control
body: <p>I want to switch between 2 UIViewController classes programmatically without any extra UI control like a UITabBarController that adds a UI to the application.</p>
  
  <p>My main loads the first view controller with addSubView. </p>
  
  <pre><code>    vc1 = new viewc1();
      window.AddSubview(vc1.View);
      window.MakeKeyAndVisible ();    
  </code></pre>
  
  <p>I can load my second viewcontroller from the first one with PresentModalViewController </p>
  
  <pre><code>    vc2 = new viewc2();
      PresentModalViewController(vc2, true);
  </code></pre>
  
  <p>but i need to switch back and forth, and to release the old viewControllers to save memory.
  What is the best way to do this? 
  <strong>DismissModalViewControllerAnimated(false);</strong> in the 2nd view controller isnt releasing memory and I dont want modal "windows" as it doesnt seem optimal. I have a custom UI so the tabbar controller is not wanted.</p>