Programming Tutorials

Things to note when changing a function to async in your controller

By: Linda Ng in Asp.net Tutorials on 2023-06-01  

When changing a function to an asynchronous function, there are several things to note:

1. Method signature: Change the return type of the method to Task or Task<T>, where T represents the type of the result if applicable.

2. async keyword: Add the async keyword to the method declaration.

3. await keyword: Use the await keyword before calling asynchronous operations. This indicates that the method should asynchronously wait for the operation to complete.

4. Exception handling: Consider how exceptions will be handled. Asynchronous methods can throw exceptions, so it's important to handle them appropriately using try/catch blocks or propagating them up the call stack.

5. Asynchronous alternatives: Use asynchronous alternatives for I/O-bound operations, such as ReadAsync instead of Read, WriteAsync instead of Write, etc. This allows the method to truly perform asynchronously.

6. Task cancellation: Consider supporting cancellation by using CancellationToken parameters and checking for cancellation requests using cancellationToken.IsCancellationRequested.

7. Synchronization context: Be aware of the synchronization context in which the method executes. By default, async methods capture and resume on the same context, such as the UI context in a UI application. If you need to switch the context, you can use ConfigureAwait to specify whether to resume on the captured context or not.

8. Task completion: Ensure that the asynchronous operation is properly awaited and that the returned Task is used to observe the completion of the operation. Avoid using Task.Result or Task.Wait synchronously, as it can lead to deadlocks in certain scenarios.

9. Consistency: Consider the calling code and ensure that all the necessary methods and dependencies support asynchronous patterns.

10. Testing: Update unit tests to account for the asynchronous nature of the method. Use await and Task-related assertions to properly test asynchronous code.

These are some general considerations when changing a function to an async function. However, each specific scenario may have additional considerations depending on the nature of the code and the requirements of the application.