ThreadPool.QueueUserWorkItem uses ASP.Net

Question

In Asp.Net for creating a huge pdf report iam using \"ThreadPool.QueueUserWorkItem\", My requirement is report has to be created asynchronously , and i do not want to wait f

Answer 1

The QueueUserWorkItem() method utilizes the process's ThreadPool which automatically manages a number of worker-threads. These threads are assigned a task, run them to completion, then are returned to the ThreadPool for reuse.

Since this is hosted in ASP.NET the ThreadPool will belong to the ASP.NET process.

The ThreadPool is a very good candidate for this type of work; as the alternative of spinning up a dedicated thread is relatively expensive. However, you should consider the following limitations of the ThreadPool as well:

• The ThreadPool is used by other aspects of .NET, and provides a limited number of threads. If you overuse it there is the possibility your tasks will be blocked waiting for others to complete. This is especially a concern in terms of scalability--however it shouldn't dissuade you from using the ThreadPool unless you have reason to believe it will be a bottleneck.

• The ThreadPool tasks must be carefully managed to ensure they are returned for reuse. Unhandled exceptions or returns from a background thread will essentially "leak" that thread and prevent it from being reused. In these scenarios the ThreadPool may effectively lose it's threads and cause a serious slowdown or halt of the process.

• The tasks you assign to the ThreadPool should be short-lived. If your processing is intensive then it's a better idea to provide it with a dedicated thread.

All these topics relate to the simple concept that the ThreadPool is intended for small tasks, and for it's threads to provide a cost-saving to the consuming code by being reused. Your scenario sounds like a reasonable case for using the ThreadPool--however you will want to carefully code around it, and ensure you run realistic load-tests to determine if it is the best approach.