TaskCompletionSource – Trying to understand threadless async work

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TaskCompletionSource is used to create Task objects that don’t execute code.

They’re used quite a bit by Microsoft’s new async APIs – any time there’s I/O-based asynchronous operations (or other non-CPU-based asynchronous operations, like a timeout). Also, any async Task method you write will use TCS to complete its returned Task.

I have a blog post Creating Tasks that discusses different ways to create Task instances. It’s written from an async/await perspective (not a TPL perspective), but it still applies here.

Also see Stephen Toub’s excellent posts:

  • The Nature of TaskCompletionSource
  • Mechanisms for Creating Tasks
  • await anything; (using TaskCompletionSource to await anything).
  • Using Tasks to implement the APM Pattern (creating Begin/End using TaskCompletionSource).

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