How to wait correctly until BackgroundWorker completes?

Solution 1:

Try using the AutoResetEvent class like this:

var doneEvent = new AutoResetEvent(false);
var bw = new BackgroundWorker();

bw.DoWork += (sender, e) =>
{
  try
  {
    if (!e.Cancel)
    {
      // Do work
    }
  }
  finally
  {
    doneEvent.Set();
  }
};

bw.RunWorkerAsync();
doneEvent.WaitOne();

Caution: You should make sure that doneEvent.Set() is called no matter what happens. Also you might want to provide the doneEvent.WaitOne() with an argument specifying a timeout period.

Note: This code is pretty much a copy of Fredrik Kalseth answer to a similar question.

Solution 2:

To wait for a background worker thread (single or multiple) do the following:

1. Create a List of Background workers you have programatically created:

   private IList<BackgroundWorker> m_WorkersWithData = new List<BackgroundWorker>();
   

2. Add the background worker in the list:

   BackgroundWorker worker = new BackgroundWorker();
   worker.DoWork += new DoWorkEventHandler(worker_DoWork);
   worker.ProgressChanged += new ProgressChangedEventHandler(worker_ProgressChanged);
   worker.WorkerReportsProgress = true;
   m_WorkersWithData.Add(worker);
   worker.RunWorkerAsync();
   

3. Use the following function to wait for all workers in the List:

   private void CheckAllThreadsHaveFinishedWorking()
   {
       bool hasAllThreadsFinished = false;
       while (!hasAllThreadsFinished)
       {
           hasAllThreadsFinished = (from worker in m_WorkersWithData
                                    where worker.IsBusy
                                    select worker).ToList().Count == 0;
           Application.DoEvents(); //This call is very important if you want to have a progress bar and want to update it
                                   //from the Progress event of the background worker.
           Thread.Sleep(1000);     //This call waits if the loop continues making sure that the CPU time gets freed before
                                   //re-checking.
       }
       m_WorkersWithData.Clear();  //After the loop exits clear the list of all background workers to release memory.
                                   //On the contrary you can also dispose your background workers.
   }