Debugging WinRT Apps: Why the Suspend Event Might Not Fire

The Suspending event is critical for Windows Phone 8.1 apps, enabling state preservation before suspension. However, during debugging, this event may not trigger, causing testing difficulties.

Consider this example:

/// 

/// Initializes the singleton application object.
/// 
public App()
{
    ...
    Suspending  = OnSuspending;
}

/// 

/// Suspend handling method.
/// 
private void OnSuspending(object sender, SuspendingEventArgs e)
{
    var deferral = e.SuspendingOperation.GetDeferral();
    deferral.Complete();
}

Breakpoints in OnSuspending remain unhit during debugging. This is expected; the Suspending event is designed for non-debugging suspension scenarios.

Debugging and Suspension: A Closer Look

Windows Phone 8.1 prevents the Suspending event from firing while debugging to maintain app activity for inspection. This necessitates alternative testing methods.

To simulate suspension, utilize Visual Studio's Debug Location toolbar. Select "Suspend" from the Lifecycle events dropdown to manually trigger the event. After adjustments, select "Resume" to resume app execution. This allows for testing suspension handling logic without deploying the app.

Effective Suspension Testing Strategies

Thorough suspension handling testing requires a non-debugging environment. Deploying to an emulator or physical device simulates real-world suspension and resumption, verifying the app's behavior under these conditions.