However the computation thread usually has to provide evidence that it has done something and this means that it has to interact with the UI components.

As is well known, UI components aren't threadsafe - hence the rule that only the thread that created a component can access it.

This is extract from MSDN Code Project A simple WPF application which reads 12MB text file, then loops through and returns unique words with count of its occurrences in text file.

Instead of using Thread Sleep or Http Client to demonstrate async await, I have word count kind of example.

The proper solution is to use a new thread to do all of the heavy computation and leave the UI thread free to get on with what it is supposed to do - deal with user events.

I also recommend this rule be applied to any synchronous blocks of code; if they are likely to take more than 50ms, push them onto the thread pool via in your library code, and only run continuations on the UI thread if they actually need a UI context.

But how many continuations can the UI thread really be expected to handle?

As the new API is damn simple, it made the WPF to support it as well.

The first thing that has been introduced to support the async update is the introducion to new method Invoke and Invoke Async to the Dispatcher.