Can I set more than one trigger for a BackgroundTask of UWP?

Question

I cannot find in the MSDN documentation if I can set only one trigger (with SetTrigger() method) to a background task or multiple. What if I want to trigger the task on a timer and also programmatically and thus I would need TimerTrigger and ApplicationTrigger? Also is it possible to set multiple conditions with AddCondition()?

Answer 1

A background task registration can only have a single trigger but, you can have several registration for the same background task.

You can have as many conditions as you want.

For example, here, MyBackgroundTask is triggered both by a TimeTrigger and an UserPresent triggers when an Internet connection is available. MyBackgroundTask.Run() will be called in both cases.

public sealed class MyBackgroundTask : IBackgroundTask
{
    public void Run(IBackgroundTaskInstance taskInstance)
    {
        // your task code here
    }

    public void Register()
    {
         RegisterWithTrigger(BackgroundTaskSuffixTime,          new TimeTrigger((uint) RefreshInterval.TotalMinutes, false));
         RegisterWithTrigger(BackgroundTaskSuffixUserPresent,   new SystemTrigger(SystemTriggerType.UserPresent, false));
    }

    private static IBackgroundTaskRegistration RegisterWithTrigger(string taskSuffix, IBackgroundTrigger trigger)
    {
        var taskEntryPoint  = typeof(MyBackgroundTask).FullName;
        var taskName        = taskEntryPoint + taskSuffix;

        var registration            = BackgroundTaskRegistration.AllTasks.Select(x => x.Value).FirstOrDefault(x => x.Name == taskName);
        if(registration != null) return registration;

        var taskBuilder             = new BackgroundTaskBuilder();
        taskBuilder.Name            = taskName;
        taskBuilder.TaskEntryPoint  = taskEntryPoint;
        taskBuilder.SetTrigger(trigger);
        taskBuilder.AddCondition(new SystemCondition(SystemConditionType.InternetAvailable));
        return taskBuilder.Register();
    }
}

Do not forget to declare all the appropriate triggers in the application manifest:

<Extension Category="windows.backgroundTasks" EntryPoint="Background.MyBackgroundTask">
  <BackgroundTasks>
    <Task Type="systemEvent" />
    <Task Type="timer" />
  </BackgroundTasks>
</Extension>