Windows Phone Background Agents - windows-phone-8

Question

Question on agents: I specifically want to create a Periodic Task, but only want to run it once every day, say 1am, not every 30 minutes which is the default. In the OnInvoke, do I simply check for the hour, and run it only if current hour matches that desired hour.
But on the next OnInvoke call, it will try to run again in 30 minute, maybe when it's 1:31am.
So I guess I'd use a stored boolean in the app settings to mark as "already run for today" or similar, and then check against that value?

Answer 1

If you specifically want to run a custom action at 1 am, i'm not sure that a single boolean would be enough to make it work.
I guess that you plan to reset your boolean at 1:31 to prepare the execution of the next day, but what if your periodic task is also called at 1h51 (so called more than 2 times between 1am and 2am).
How could this happen? Well maybe this could happen if the device is reboot but i'm not quiet sure about it. In any case, storing the last execution datetime somewhere and comparing it to the current one can be a safer way to ensure that your action is only invoked once per day.
One question remains : Where to store your boolean or datetime (depending which one you'll pick)?
AppSetting does not seem to be a recommanded place according msdn :
Passing information between the foreground app and background agents
can be challenging because it is not possible to predict if the agent
and the app will run simultaneously. The following are recommended
patterns for this.
For Periodic and Resource-intensive Agents: Use LINQ 2 SQL or a file in isolated storage that is guarded with a Mutex. For
one-direction communication where the foreground app writes and the
agent only reads, we recommend using an isolated storage file with a
Mutex. We recommend that you do not use IsolatedStorageSettings to
communicate between processes because it is possible for the data to
become corrupt.
A simple file in isolated storage should get the job done.

Answer 2

If you're going by date (once per day) and it's valid that the task can run at 11pm on a day and 1am the next, then after the agent has run you could store the current date (forgetting about time). Then whenever the agent runs again in 30 minutes, check if the date the task last ran is the same as the current date.
protected override void OnInvoke(ScheduledTask task)
{
var lastRunDate = (DateTime)IsolatedStorageSettings.ApplicationSettings["LastRunDate"];
if(DateTime.Today.Subtract(lastRunDate).Days > 0)
{
// it's a greater date than when the task last ran
// DO STUFF!
// save the date - we only care about the date part
IsolatedStorageSettings.ApplicationSettings["LastRunDate"] = DateTime.Today;
IsolatedStorageSettings.ApplicationSettings.Save();
}
NotifyComplete();
}