Create a completed Task

Question

I want to create a completed Task (not Task<T>). Is there something built into .NET to do this?

A related question: Create a completed Task<T>

Answer 1

The newest version of .Net (v4.6) is adding just that, a built-in Task.CompletedTask:

Task completedTask = Task.CompletedTask; 

That property is implemented as a no-lock singleton so you would almost always be using the same completed task.

Answer 2

Task<T> is implicitly convertable to Task, so just get a completed Task<T> (with any T and any value) and use that. You can use something like this to hide the fact that an actual result is there, somewhere.

private static Task completedTask = Task.FromResult(false); public static Task CompletedTask() {     return completedTask; } 

Note that since we aren't exposing the result, and the task is always completed, we can cache a single task and reuse it.

If you're using .NET 4.0 and don't have FromResult then you can create your own using TaskCompletionSource:

public static Task<T> FromResult<T>(T value) {     var tcs = new TaskCompletionSource<T>();     tcs.SetResult(value);     return tcs.Task; }