Upgrading Windows Phone 7 app to Mango

I want to test the fast app switching and some other new features introduced in Windows phone Mango with my existing Windows Phone 7 app. I have installed Mango developer tools, but if I open my existing windows phone 7 app and try to use Mango SDK functions, it is not allowing me to use those functions. Can anyone tell me how to u开发者_C百科pgrade a Windows Phone 7 App into Windows Phone Mango ?.

In Visual Studio, open the existing solution. In Solution Explorer, right-click the Windows Phone project(s), and then click Upgrade to Windows Phone 7.1.