How to Suspend and Resume Asynchronous Operations in C#/XAML Metro Apps?

Managing Asynchronous Tasks in C#/XAML Metro Style Apps

In C#/XAML Metro style applications, handling long-running operations asynchronously using async/await is crucial to prevent UI freezes. However, situations arise where pausing and resuming these operations based on user interaction is needed.

Utilizing SemaphoreSlim for Event-Driven Pausing

The SemaphoreSlim class offers an elegant solution for event-based suspension:

1. Initialize a SemaphoreSlim object with an initial count of 0 and a maximum count of 1: private SemaphoreSlim signal = new SemaphoreSlim(0, 1);
2. Upon a "continue" button click, release the semaphore: signal.Release();
3. Within your long-running method (e.g., GetResults), wait for the semaphore signal: await signal.WaitAsync();

Employing TaskCompletionSource<bool> for Task Management

Another effective approach involves the TaskCompletionSource<bool> class:

1. Declare a TaskCompletionSource<bool>: private TaskCompletionSource<bool> tcs = new TaskCompletionSource<bool>();
2. On the "continue" button click, set the task's result: tcs.SetResult(true);
3. In your asynchronous operation, await the task: await tcs.Task;

Advantages of Event-Driven Pause/Resume

These methods avoid the inefficiencies of polling, eliminating busy-waiting and resource waste. By employing event-driven mechanisms, you achieve efficient pause and resume functionality for long-running asynchronous tasks.

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