Example for Multiple Levels of Namespace

using System; 
using System.Collections.Generic; 
using System.IO; 
using System.Linq; 
using Windows.Foundation; 
using Windows.Foundation.Collections; 
using Windows.UI.Xaml; 
using Windows.UI.Xaml.Controls; 
using Windows.UI.Xaml.Controls.Primitives; 
using Windows.UI.Xaml.Data; 
using Windows.UI.Xaml.Input; 
using Windows.UI.Xaml.Media; 
using Windows.UI.Xaml.Navigation;

namespace App2 
{     
   namespace App1     
   {         
      namespace App3         
      {             
         class A             
         {             
         }         
      }

   } 
}