Differences between ScheduledTaskAgent for Windows Phone 8 and 7.1 - silverlight

Question

I have a big problem.
I wrote an app for Windows Phone 7.1+, and it's also published on Windows Phone Store:
this app works well for Windows Phone 7.1 and also for Windows Phone 8, and there were no problems during app submission process (who also declares that my app is fully compatible with any OS since Windows Phone 7.5).
The problem is related only to my Scheduled Agent, which runs perfectly on Windows Phone Mango (7.1), but it is not firing at all on Windows Phone 8 (I've also tested my app on real devices, with both the OS').
When I upgraded to Visual Studio 2012 (Express for Windows Phone), I've noticed that it is possibile to add two different types of ScheduledTaskAgent project: one for Windows Phone 7.5 and one for Windows Phone 8 (obviously it wasn't so in Visual Studio 2010...and I used the only one available = the first) !
Dou you think this can be the reason while the scheduled agent is not working in WP8?
What's the difference between the two projects types?
How to manage (in code I mean) two projects of that type? Is it possible?
How can I choose which task I have to register (see code below)?
Will the submission process fail with two ScheduledTaskAgent projects (I think so)?
This is the critical part of the code, when I'm registering my task at startup:
PeriodicTask newTask = new PeriodicTask("MyTaskID");
newTask.Description = "my Description";
ScheduledActionService.Add(newTask);
#if DEBUG
Microsoft.Phone.Scheduler.ScheduledActionService.LaunchForTest("MyTaskID", TimeSpan.FromSeconds(5));
#endif
Thank you in advance.

Answer 1

The only difference between the two project types is (1) the Windows Phone 8 one targets Windows Phone 8 instead of 7.1 and (2) it references the Windows Phone 8 SDK instead of the Windows Phone 7 dlls.
I have an application where I have two projects (7.1 and 8.0). I also have two background agent projects (7.1 and 8.0) and I share code between them using linked files. I reference the 8.0 agent from the 8.0 project and the 7.1 agent from the 7.1 project. I used this example as a best practice for having the two versions of code.
You do not want to reference two agents since that will not work.
If you remove the #if DEBUG does your agent get called when you're debugging?

Answer 2

First make sure you got the proper reference in app manifest file.
<ExtendedTask Name="BackgroundTask">
<BackgroundServiceAgent Specifier="ScheduledTaskAgent" Name="MyApp.Agent" Source="MyApp.Agent" Type="MyApp.Agent.ScheduledAgent" />
</ExtendedTask>
Second the Agent library must be referenced in the main app project.
Third, make sure you are not exceeding the allowed running time or memory allocation. In WP8 the cap for background agent was raised to 11MB. Also there is a limit of app with registered background tasks, so it might be possible that there was no free slot for your task with bg agent.