title: Xamarin FindViewById returns null
body: <p>I am trying to make an android app using Xamarin so C#. I made two layouts and in each one of them I made tow buttons to navigate between them.I tried like this:</p>
  <pre><code>using System;
  
  using Android.App;
  using Android.OS;
  using Android.Views;
  using Android.Widget;
  
  
  namespace Example
  {
      [Activity(Label = &quot;Example&quot;, MainLauncher = true, Icon = &quot;@drawable/icon&quot;)]
      public class MainActivity : Activity
      {
          protected override void OnCreate(Bundle bundle)
          {
              base.OnCreate(bundle);
              this.SetContentView(Resource.Layout.Main);
  
              this.FindViewById&lt;Button&gt;(Resource.Id.ForwardButton).Click += this.Forward;
              this.FindViewById&lt;Button&gt;(Resource.Id.BackButton).Click += this.Back;
          }
  
          public void Forward(object sender, EventArgs e)
          {
              this.SetContentView(Resource.Layout.Main2);
          }
  
          public void Back(object sender, EventArgs e)
          {
              this.SetContentView(Resource.Layout.Main);
          }
      }
  }
  </code></pre>
  <p>But every time when I start the app I get this errror: System.NullReferenceException has been thrown.Object reference not set to an instance of an object. Any advice or better idea?</p>