title: The type or namespace name 'Xamarin' missing error in Xamarin Studio
body: <p>I'm getting this error:  </p>
  
  <blockquote>
    <p>"MyApp\App.cs(7,7): Error CS0246: The type or namespace name 'Xamarin'
    could not be found (are you missing a using directive or an assembly
    reference?) (CS0246)".</p>
  </blockquote>
  
  <p>I'm using Xamarin Studio to make a cross platform app via Xamarin.Forms. Whenever I build the basic form project I get this error and I don't know why.  </p>
  
  <p>I'm new in Xamarin.  </p>
  
  <p>Here is the code of app.cs:</p>
  
  <pre class="lang-cs prettyprint-override"><code>using System;
  using Xamarin.Forms;             //This is the line where error occurs
  
  namespace FIrstFormProject
  {
      public class App
      {
          public static Page GetMainPage ()
          {
              return new ContentPage 
              {
                  Content = new Label 
                  {
                      Text = "Hello, Forms !",
                      VerticalOptions = LayoutOptions.CenterAndExpand,
                      HorizontalOptions = LayoutOptions.CenterAndExpand,
                  },
              };
          }
      }
  }
  </code></pre>