How to repeat Background Task Timer? - windows-phone

Question

I have a Windows Phone project. I want to run a background task three times, and automatically unregister after it has run three times.
My code:
var taskRegisted = false;
var exampleTaskName = "TimerRegister";
foreach (var task in BackgroundTaskRegistration.AllTasks)
{
if (task.Value.Name == exampleTaskName)
{
taskRegisted = true;
break;
}
}
if (taskRegisted == false)
{
var builder = new BackgroundTaskBuilder();
//var trigger = new SystemTrigger(SystemTriggerType.TimeZoneChange, false);
var trigger = new TimeTrigger(15, false);
builder.Name = exampleTaskName;
builder.TaskEntryPoint = typeof(ToastTask).FullName;
builder.SetTrigger(trigger);
var taskRegistion = builder.Register();
taskRegistion.Completed += taskRegistion_Completed;
}
My code runs every fifteen minutes, and I want it to run only three times.

Answer 1

It's unfortunately not possible to limit the number of times a background task will run in the manner you describe. The TimeTrigger does have the 'OneShot' property allowing you to have the task run only once, but it can't be configured to run X times, either 1 or infinite.
My suggestion would be to track the number of times your task has been run. Just write to a file in Isolated Storage with the number of times your task has run, and then check that value when your task starts up. After doing this if you've run 3 times return out of your Run() method without doing any real 'work'.

Answer 2

Nothing stands on your way to unregister your BackgroundTask inside the Run method (BackgroundTask's). For example the below code should run three times and then unregister itself:
// code in Run method:
int nrPreviousRuns = 0;
var settings = ApplicationData.Current.LocalSettings;
if (settings.Values.ContainsKey("numberOfRuns")) nrPreviousRuns = (int)settings.Values["numberOfRuns"];
if (nrPreviousRuns >= 3) // maksimum number of runs
{
// unregister the task
foreach (var cur in BackgroundTaskRegistration.AllTasks)
if (cur.Value.Name == "yourBGTaskName") cur.Value.Unregister(true);
settings.Values.Remove("numberOfRuns");
}
else settings.Values["numberOfRuns"] = ++nrPreviousRuns;