How to make BackgroundWorker ProgressChanged events execute in sequence?

Question

Consider the following code:

private static BackgroundWorker bg = new BackgroundWorker();

static void Main(string[] args) {
  bg.DoWork += bg_DoWork;
  bg.P         


        

Answer 1

Do not use this solution!!! May lead to deadlocks as SLaks has pointed it out.

I seem to have stumbled upon an answer. I changed the code the following way:

   [MethodImpl(MethodImplOptions.Synchronized)]
   static void bg_ProgressChanged(object sender, ProgressChangedEventArgs e) {
     Console.WriteLine(e.ProgressPercentage);
     Thread.Sleep(100);
     Console.WriteLine(e.ProgressPercentage);
   }

and now I get the output I want:

0 0 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9

Answer 2

BackgroundWorker raises ProgressChanged events on the current SynchronizationContext of the thread that called RunWorkerAsync().

The default SynchronizationContext runs callbacks on the ThreadPool without any synchronization.

If you use BackgroundWorker in a UI application (WPF or WinForms), it will use that UI platform's SynchronizationContext, which will execute callbacks in order.