title: Why does FindViewById return null when switching from portrait to landscape?
body: <p>The InitView method of one of my activities calls its property</p>
  
  <pre><code>protected ListView MainMenu
      {
          get
          {
              return FindViewById&lt;ListView&gt;(Resource.Id.mainmenu);
          }
      }
  </code></pre>
  
  <p>...which refers to a ListView defined as part of a RelativeLayout "MainMenuLayout.axml" located in the "layout" folder in my Android project:</p>
  
  <pre><code>    &lt;ListView
      android:id="@+id/mainmenu"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:choiceMode="singleChoice"
      android:layout_below="@id/mainmenuHeader"
      android:divider="#e5e5e5"
      android:dividerHeight="1dp"
      android:background="#fff" /&gt;
  </code></pre>
  
  <p>When in Portrait mode, this works as expected. However, when switching to landscape mode, the call to FindViewById above returns null. It is my understanding that Android should use the layout folder for both portrait and landscape mode. Resource.designer.cs also contains</p>
  
  <pre><code>public const int mainmenu = 2131492931;
  </code></pre>
  
  <p>as expected. Notably, manually handling orientation changes by setting ConfigurationChanges = ConfigChanges.Orientation and ConfigChanges.ScreenSize causes landscape mode to work correctly. Is this a Xamarin issue, or am I misunderstanding something?</p>