Do I Need to Dispose of Fire-and-Forget TPL Tasks?

Not Disposing TPL Tasks: Consequences and Alternate Solutions

When triggering a task to run in the background without waiting for its completion, the common use of Task.Factory.StartNew() raises questions about the necessity of calling Dispose() on the returned Task object. While MSDN recommends disposing of all tasks, the issue of disposing tasks in this specific scenario is often overlooked.

Regarding the consequences of not disposing, Stephen Toub, a Microsoft PFX team member, clarifies that Task.Dispose() exists to handle an event handle used in certain waiting scenarios. However, when continuations are the primary means of accessing the task, this event handle will never be allocated. Stephen Toub suggests relying on finalization to manage these tasks.

Official documentation on this topic is limited. However, Stephen Toub's blog post, "Do I need to dispose of Tasks?," expands on this issue and highlights improvements introduced in .Net 4.5.

In general, you don't need to dispose of Task objects most of the time. Reasons to dispose include freeing unmanaged resources promptly and avoiding the finalizer cost. However, these considerations do not typically apply to Task objects:

• In .Net 4.5 and later, internal wait handles are only allocated when using IAsyncResult.AsyncWaitHandle explicitly.
• Task objects themselves have no finalizers; the wait handle is wrapped in an object with a finalizer, which is only run if the handle is allocated.

Alternate methods for fire-and-forget tasks with TPL:

If disposing of task objects is still a concern, there are alternative approaches:

• Use the ThreadPool.QueueUserWorkItem() method in .Net 3.5 or later.
• Create a Task without returning it: Task.Run(() => DoSomething());.
• Use the Task.ContinueWith method to attach a continuation that will perform automatic cleanup.

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