Why async functions are called twice?

Question

I\'m using Threading timer to do some periodic job:

private static async void TimerCallback(object state)
{
        if (Interlocked.CompareExchange(ref curre         


        

Answer 1

I think I know WHY ! In two words: - reason that function with await impliciti create a callback thread. Better you can see how explain it Jeffrey Richter on this video https://wintellectnow.com/Videos/Watch?videoId=performing-i-o-bound-asynchronous-operations from 00:17:25

just try it:

var tasksRead = Enumerable.Range(3, 35).Select(i => ReadSensorsAsync(i));
var tasksRecord = tasksRead.Where(x => x.Result != null).Select(x => RecordReadingAsync(x.Result));

await Task.WhenAll(tasksRead);

await Task.WhenAll(tasksRecord);