Windows Service running Async code not waiting on work to complete

Question

In Brief

I have a Windows Service that executes several jobs as async Tasks in parallel. However, when the OnStop is called, it seems that these are a

Answer 1

Your problem is that OnStop is async void. So, when it does await this.AllJobsCompleted, what actually happens is that it returns from OnStop, which the SCM interprets as having stopped, and terminates the process.

This is one of the rare scenarios where you'd need to block on a task, because you cannot allow OnStop to return until after the task completes.

This should do it:

protected override void OnStop()
{
  this.RequestAdditionalTime(100000); // some large number        
  _cancelSource.Cancel();     
  TraceMessage("Task cancellation requested."); // Last thing traced

  try
  {
    bool allStopped = this.AllJobsCompleted.GetAwaiter().GetResult();          
    TraceMessage(string.Format("allStopped = '{0}'.", allStopped));
  }
  catch (Exception e)
  {
    TraceMessage(e.Message);
  }
}