With the updated SDK, Microsoft also added additional application types that are avilable for developers in Visual Studio. In this short article, I am going to go over the new application types and their purpose.

First of all, take a look at the list of Silverlight-based applications:

Then, open the XNA Game Studio 4.0 category and see what's added there:

New Silverlight-based applications include:

• Windows Phone 3D Graphics Application - the application type used to invoke XNA content from a Silverlight application. The idea behind this application is to have a pre-built XAML page that has a game loop and that is calling an included XNA project. This can be considered a pure demo of Silverlight-XNA interop.
• Windows Phone Audio Playback Agent - a non-UI project time that creates a class based on AudioPlayerAgent. Consider this some sort of a class library, but that will later be tied to a BackgroundAudioPlayer to handle custom events.
• Windows Phone Audio Streaming Agent - similar to the audio playback agent, this project is used to create a class that will be used with an application that implements a streaming mechanism coupled with a background player.
• Windows Phone Task Scheduler Agent - a project that will create a class based on ScheduledTaskAgent that will allow developers to handle task invocation events for existing scheduled tasks.

Three new project types introduce the concept of agents. If you've never heard about those before, you can read more about them here:

• How to: Play Background Audio for Windows Phone
• Scheduled Tasks Overview for Windows Phone

The only new XNA project is called Windows Phone Rich Graphics Application.It has pretty much the same concept as the Windows Phone 3D Graphics Application. The developer is able to invoke a XNA-rendering page from inside an existing Silverlight application. I am not entirely sure why there is a need for two different instances of the same project type, but I guess this will be sorted out in the final release of the developer tools.