Wait for QueueUserWorkItem to Complete

Question

If I add jobs to the thread pool with QueueUserWorkItem... how do I keep my program from going forward until all jobs are completed?

I know I could add some logic to keep the app from running until all jobs are completed, but I want to know if there is something like Thread.Join() or if there's any way to retrieve each thread that is being assigned a job.

Answer 1

You could use events to sync. Like this:

private static ManualResetEvent resetEvent = new ManualResetEvent(false);  public static void Main() {     ThreadPool.QueueUserWorkItem(arg => DoWork());     resetEvent.WaitOne(); }  public static void DoWork() {     Thread.Sleep(5000);     resetEvent.Set(); } 

If you don't want to embed event set into your method, you could do something like this:

var resetEvent = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(     arg =>      {         DoWork();         resetEvent.Set();     }); resetEvent.WaitOne(); 

For multiple items:

var events = new List<ManualResetEvent>();  foreach(var job in jobs) {        var resetEvent = new ManualResetEvent(false);     ThreadPool.QueueUserWorkItem(         arg =>         {             DoWork(job);             resetEvent.Set();         });     events.Add(resetEvent); } WaitHandle.WaitAll(events.ToArray());