C#：Task.Run 在主线程上执行

Question

I am using monotouch/Xamarin for an iOS app.

The documentation for Task.Run states:

Queues the specified work to run on the ThreadPool and returns a task handle for that work.

Which essentially indicates that it could run on any thread ThreadPool .

I want to do something like:

Task.Run(async () => await PerformTask());

but have it run on the main thread. Normally I would write it using BeginInvokeOnMainThread as follows:

BeginInvokeOnMainThread(async () => await PerformTask());

But I am doing this in shared code and do not want to use iOS specific calls. Is there a way for me to tell Task.Run() to invoke the action on the main thread?

Answer 1

If you want to run PerformTask in the current thread, instead of a thread pool thread, you simply need to not call Task.Run . Just use:

PerformTask();

and you're done. If you want to only continue executing the rest of the method when that task is done, then await it:

await PerformTask();

There is no reason to call Task.Run here for you, nor is there any reason to create a lambda that awaits the method for no particular reason (you could just call it directly if you wanted to start it from a thread pool thread).

Answer 2

Have a look at MainQueue.cs:https://gist.github.com/gering/0aa9750d3c7d14b856d0ed2ba98374a8

It is for Xamarin Forms applications. You have to call Init() from main thread once, but then you are able to ensure execution on main thread.