The thread pool in .NET resides in the System.Threading.ThreadPool class. Generally, there is a lot of discussion around creating your own threads, as opposed to using the thread pool. Popular thinking dictates that the thread pool should be used for brief jobs. This is because the thread pool is limited in size. There are many other processes in the system that will use the thread pool. You, therefore, do not want your application to hog all the threads in the thread pool.

The rule is that you can't set the number of maximum worker or completion threads to be fewer than the number of processors on your computer. You are also not allowed to set the maximum worker or completion threads to less than the minimum thread pool size.