How Do You Cancel an async Method? | Step-by-Step Tutorial

Step-by-Step Tutorial: How to Cancel an Async Method

1. Understand the Need for Asynchronous Programming:

• Writing asynchronous code involves several aspects that need to be considered.
• Asynchrony is important to prevent blocking the main thread of execution, especially during I/O operations.

2. Design an Asynchronous Operation:

• Design an asynchronous operation that supports graceful cancellation.
• Ensure that the operation interacts with the file system and performs tasks such as writing chunks of text to a file.

3. Implement Async Methods and Tasks:

• Utilize async methods and Tasks in .NET for asynchronous programming.
• Modify the custom method to be async and return a Task, allowing for asynchronous execution.

4. Separate UI Interaction and Background Task:

• Take the Task but do not await it to keep the UI responsive.
• Perform regular UI work while occasionally checking the status of the background task.

5. Implement Cancellation Tokens:

• Tasks in .NET support cancellation tokens for gracefully canceling asynchronous tasks.
• Create a cancellation token source and pass the cancellation token to the asynchronous method.

6. Check Cancellation Token within Async Method:

• Ensure to check the cancellation token within the async method to handle cancellation gracefully.
• Clean up resources if the OperationCancelledException is thrown.

7. Proper Coding Pattern with Cancellation Tokens:

• Follow the coding pattern to check the cancellation token periodically and handle cancellation exceptions appropriately.
• Clean up resources in a try-finally block to ensure proper resource management.

8. Handle Cancellation Gracefully:

• Handle cancellation as a decision rather than an error.
• Stop the propagation of OperationCanceledException once cancellation is signaled.

9. Test Cancellation Functionality:

• Run the application and interact with it to test the cancellation functionality.
• Confirm that the operation was canceled and that resources were cleaned up efficiently.

10. Explore Progress Signaling:

• Consider learning how to signal progress back from asynchronous operations for further enhancement.

By following these steps, you can effectively implement cancellation functionality in your async methods and ensure graceful handling of asynchronous operations.