deadlock even after using ConfigureAwait(false) in Asp.Net flow

Question

I\'m hitting deadlock even after using ConfigureAwait(false), below is the sample code.

As per the sample http://blog.stephencleary.com/2012/02/async-a

Answer 1

From the comments:

I was under assumption, once ConfigureAwait(false) is used (any where in the call stack), execution from that point will not cause deadlock.

I don't believe in black magic, and neither should you. Always strive to understand what happens when you use something in your code.

When you await an async method that returns a Task or a Task, there is an implicit capture of the SynchronizationContext by the TaskAwaitable being generated by the Task.GetAwaiter method.

Once that sync context is in place and the async method call completes, the TaskAwaitable attempts to marshal the continuation (which is basically the rest of the method calls after the first await keyword) onto the SynchronizationContext (using SynchronizationContext.Post) which was previously captured. If the calling thread is blocked, waiting on that same method to finish, you have a deadlock.

You should ask yourself Should I expose synchronous wrappers for asynchronous methods? 99 percent of the time the answer is no. You should use a synchronous API, such as the one WebClient offers.