How and when to use ‘async’ and ‘await’

Question

From my understanding one of the main things that async and await do is to make code easy to write and read - but is using them equal to spawning background threads to perfo

Answer 1

Tasks let you control the number of threads you are running on.
The optimal number of threads is the number of cores you have.

• when your app is Console, WinForms or WPF then you are normally running on a single-thread.

  • in this case you want to increase the number of threads
  • your main tool is Task.Run(), and sometimes Parallel.ForERach()
  • doing synchronous I/O on a thread (with Task.Run()) is sub-optimal but acceptable

• when your app runs on a Webserver it normally is running on (too) many threads.
  asp.net waits for incoming requests and quickly hands each one to a new pool thread.

  • in this case you want to decrease the number of threads
  • your main tool is to await asynchrous I/O
  • make sure you have an unbroken await chain from your async Action method down to the actual I/O
  • doing synchronous I/O or CPU intensive work on a thread (with Task.Run()) is a de-optimization.