Should I Dispose of Fire-and-Forget Tasks in the TPL?

Fire-and-Forget Tasks with the Task Parallel Library: Disposal Concerns

When triggering fire-and-forget tasks with the Task Parallel Library (TPL), developers commonly face questions about proper disposal of Task objects. While the MSDN documentation emphasizes the need to call Dispose() before releasing the last reference, the practical implications of not doing so have been unclear.

According to Microsoft's Stephen Toub, Task disposal exists primarily to handle potentially unmanaged resources used when waiting for task completion. However, in scenarios where only continuations are used (as in fire-and-forget tasks), this event handle is not allocated.

In a recent blog post, Toub further clarifies that in .Net 4.5, the internal wait handle is only allocated when explicitly retrieving the IAsyncResult.AsyncWaitHandle property. Moreover, the Task object itself does not have a finalizer; instead, the handle is encapsulated within an object with a finalizer. Unless the handle is allocated, no finalizer will be invoked.

Summary

Based on these insights:

• Is it acceptable to not call Dispose() on the Task class in this case?

In most cases, yes, it is acceptable to not call Dispose(). The finalizer will handle cleanup.

• Is there any documentation that discusses this?

Yes, Stephen Toub's blog post provides detailed explanations.

• Is there an appropriate way of disposing of the Task object that I've missed?

Calling Dispose() is not necessary in most scenarios.

• Is there another way of doing fire & forget tasks with the TPL?

No, the pattern of using Task.Factory.StartNew() is the suggested approach for fire-and-forget tasks.

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