Aync/Await action within Task.Run()

Question

Task.Run(()=>{}) puts the action delegate into the queue and returns the task . Is there any benefit of having async/await within the Task.Run() ? I underst

Answer 1

In the example that you linked the main thread is being blocked until the asynchronous operation is done. It's being blocked by calling Wait() (which by the way is generally a bad idea).

Let's have a look at the return from the DownloadStringAsync in the linked sample:

return Task.Run(async () =>
{
    content = await new WebClient().DownloadStringTaskAsync(address);
    cachedDownloads.TryAdd(address, content);
    return content;
});

Why would you wrap this in a Task? Think about your options for a second. If you don't want to wrap this in a Task, how would you make sure the method returns a Task and still have it work? You'd mark the method as async of course! However, if you mark your method as async and you call Wait on it, you'll most likely end up with a deadlock, since the main thread is waiting for the work to finish, and your blocking the main thread so it can't let you know it's done.

When marking a method as async, the state machine will run on the calling thread, in your example however, the state machine runs on a separate thread, meaning there is little to no work being done on the main thread.