Windows Phone 7.5 XNA Game Orientation in Mixed Mode

Introduction

Maybe this will save someone some time.
 
When you create a Windows Phone Silverlight and XNA project, the XNA part will be set to Portrait mode.
To change it to Landscape, you need to:

• Set orientation of XNA page to landscape
• Replace in App.xaml:

  <xna:SharedGraphicsDeviceManager/>

  with:

  <xna:SharedGraphicsDeviceManager PreferredBackBufferWidth="800" 
  PreferredBackBufferHeight="480"  />

  if all of your XNA pages will be in this resolution. If not, you can set in code for each XNA page.