Best Way to Handle Async in WPF

Topic: Best Way to Handle Async in WPF

Hi everyone,

I'm working on a WPF application that needs to perform several long-running operations, such as fetching data from a remote API and processing large files. I've been using the Task Parallel Library (TPL) with `async` and `await`, which has significantly improved responsiveness.

However, I'm encountering some common issues:

• Updating UI elements from background threads.
• Handling exceptions thrown from async operations gracefully.
• Managing cancellation tokens for long-running tasks.
• Ensuring proper thread synchronization when multiple async operations complete concurrently.

What are the recommended best practices for managing asynchronous operations in WPF in 2023? Are there specific patterns or libraries (like CommunityToolkit.Mvvm's ObservableRecipient or async commands) that are particularly beneficial?

Any insights or code examples would be greatly appreciated!

// Example of current approach (simplified) async Task LoadDataAsync() { try { var data = await _apiService.GetDataAsync(); Dispatcher.Invoke(() => MyTextBlock.Text = data.ToString()); } catch (Exception ex) { MessageBox.Show($"Error: {ex.Message}"); } }

Re: Best Way to Handle Async in WPF

Hey AwesomeDev,

Great question! You're on the right track with TPL and async/await. For WPF, the key is bridging the gap between background threads and the UI thread seamlessly.

UI Updates: Instead of Dispatcher.Invoke directly, consider using await on methods that return Task and are already marshalled to the UI thread by the framework or by calling Task.Run() with a UI-context capturing lambda.

For MVVM scenarios, the CommunityToolkit.Mvvm (formerly MVVM Light) is excellent. Its RelayCommand (or AsyncRelayCommand in newer versions) handles the async/await pattern within commands elegantly. You can directly `await` your async operations within the command's execute method.

Here's a snippet using AsyncRelayCommand:

public class MyViewModel : ObservableRecipient { private readonly IApiService _apiService; public AsyncRelayCommand LoadDataCommand { get; } private string _status; public string Status { get => _status; set => SetProperty(ref _status, value); } public MyViewModel(IApiService apiService) { _apiService = apiService; LoadDataCommand = new AsyncRelayCommand(LoadDataAsync); } private async Task LoadDataAsync() { Status = "Loading data..."; try { var data = await _apiService.GetDataAsync(); // UI updates are handled automatically by AsyncRelayCommand's invocation context Status = $"Data loaded: {data}"; } catch (Exception ex) { Status = $"Error: {ex.Message}"; // Handle exceptions appropriately, perhaps log or show a user-friendly message } } }

Cancellation: Always use CancellationTokenSource and pass the token to your async methods. Update your commands to also accept a token if they are cancellable.

Exception Handling: Wrap your await calls in try-catch blocks. Consider using a central exception handler for unobserved task exceptions, but per-operation handling is usually cleaner.

CommunityToolkit.Mvvm is definitely the way to go for modern WPF development!

Re: Best Way to Handle Async in WPF

Thanks JediMaster, that `AsyncRelayCommand` example is really helpful. I was struggling with the command execution context.

One quick question regarding cancellation: if I have multiple long-running operations in a single command, how would I manage multiple cancellation tokens? Should I create a separate CancellationTokenSource for each operation?

// Example: Multiple operations within one command

async Task PerformMultipleOperationsAsync(CancellationToken token) { var cts1 = new CancellationTokenSource(); var cts2 = new CancellationTokenSource(); // Combine tokens for one parent token if needed, or manage separately var combinedToken = CancellationTokenSource.CreateLinkedTokenSource(token, cts1.Token, cts2.Token).Token; var task1 = Task.Run(async () => { /* Operation 1 */ await Task.Delay(2000, cts1.Token); }, cts1.Token); var task2 = Task.Run(async () => { /* Operation 2 */ await Task.Delay(3000, cts2.Token); }, cts2.Token); try { await Task.WhenAll(task1, task2); // ... process results ... } catch (OperationCanceledException) { /* Handle cancellation */ } catch (Exception ex) { /* Handle other errors */ } }

Is combining tokens with CreateLinkedTokenSource the standard approach here?