C# async/await Progress event on Task<> object

Question

I'm completely new to C# 5's new async/await keywords and I'm interested in the best way to implement a progress event.

Now I'd prefer it if a Progress event was on the Task<> itself. I know I could just put the event in the class that contains the asynchronous method and pass some sort of state object in the event handler, but to me that seems like more of a workaround than a solution. I might also want different tasks to fire off event handlers in different objects, which sounds messy this way.

Is there a way I could do something similar to the following?:

var task = scanner.PerformScanAsync();
task.ProgressUpdate += scanner_ProgressUpdate;
return await task;

question from:https://stackoverflow.com/questions/15408148/c-sharp-async-await-progress-event-on-task-object

Answer 1

Simply put, Task doesn't support progress. However, there's already a conventional way of doing this, using the IProgress<T> interface. The Task-based Asynchronous Pattern basically suggests overloading your async methods (where it makes sense) to allow clients to pass in an IProgess<T> implementation. Your async method would then report progress via that.

The Windows Runtime (WinRT) API does have progress indicators built-in, in the IAsyncOperationWithProgress<TResult, TProgress> and IAsyncActionWithProgress<TProgress> types... so if you're actually writing for WinRT, those are worth looking into - but read the comments below as well.