AsyncSampleController.cs

public async Task<ActionResult> Foo() { 
    
    //some sync stuff
    
    //runs the async method
    var foobar = await _someClass.GetAsync();
    
    //this continuation ends up in another thread.
    //cannot access some static instances such as HttpContext.Current
    doSomeWork();
    
    //some other stuff
}

This might be the solution?

SynchronizationContext.Current.Post((state) => {

    //...

}, TaskScheduler.FromCurrentSynchronizationContext());