Using the thread pool

Brief introduction

Creating threads is an expensive operation, and creating threads for each transient asynchronous operation can incur significant overhead.

Invoking delegates in a thread pool

1 usingSystem;2 usingSystem.Threading;3 4 namespaceChapter3.recipe15 {6     class Program7     {8         Static voidMain (string[] args)9         {Ten             intThreadId =0; One  ARunonthreadpool pooldelegate =Test; -  -             vart =NewThread (() = Test ( outthreadId)); the T.start (); - T.join (); -  -Console.WriteLine ("Thread ID: {0}", threadId); +  -             //call BeginInvoke () to run the delegate, and the callback function is called after the asynchronous operation completes +             //The BeginInvoke () call returns immediately after the worker thread in the thread pool is allowed to continue other work while the asynchronous operation is performed.  AIAsyncResult r = Pooldelegate.begininvoke ( outThreadId, Callback,"a delegate asynchronous call");  atR.asyncwaithandle.waitone ();//wait for the asynchronous operation to complete -             //in fact EndInvoke () waits for the completion of the asynchronous operation, so R. Asyncwaithandle.waitone (); not necessary. -             stringresult = Pooldelegate.endinvoke ( outThreadId, R); -             //when the asynchronous operation is complete, the callback function is placed in the thread pool, which is exactly a worker thread.  -Console.WriteLine ("thread pool worker thread ID: {0}", threadId); - Console.WriteLine (result); in  -Thread.Sleep (Timespan.fromseconds (2)); to         } +  -         Private Delegate stringRunonthreadpool ( out intthreadId); the  *         Private Static voidCallback (IAsyncResult ar)//callback function $         {Panax NotoginsengConsole.WriteLine ("starting a callback ..."); -Console.WriteLine ("State passed to a callbak: {0}", AR. asyncstate); theConsole.WriteLine ("is thread pool thread: {0}", Thread.CurrentThread.IsThreadPoolThread); +Console.WriteLine ("thread pool worker thread ID: {0}", Thread.CurrentThread.ManagedThreadId); A         } the  +  -         Private Static stringTest ( out intthreadId) $         { $Console.WriteLine ("starting ..."); -Console.WriteLine ("is thread pool thread: {0}", Thread.CurrentThread.IsThreadPoolThread); -Thread.Sleep (Timespan.fromseconds (2)); theThreadId =Thread.CurrentThread.ManagedThreadId; -             return string. Format ("thread pool worker thread ID was: {0}", threadId);Wuyi         } the     } -}

Methods such as using the Beginoperationname/endoperation method and the IAsyncResult object in. NET are called Asynchronous programming models , which are called async methods.

Using the thread pool