Does Parallel.ForEach Block?

Question

Does the .net function Parallel.ForEach block the calling thread? My guess as to the behavior is one of these:

1. Yes, it blocks until the slowest item executing

Answer 1

Number 1 is correct; Parallel.ForEach does not return until the loop has completed. If you don't want that behavior, you can simply execute your loop as a Task and run it on another thread.

Answer 2

Re your update, StartNew in a normal foreach() :

This may not be the most optimal for large collections, and you don't get a point to handle errors.

Your loggingServices probably doesn't hold thousands of items but the errorhandling remains a point .

Consider:

Task.Factory.StartNew(() => 
{
   try
   {
        Parallel.ForEach(loggingServices, l => l.LogMessage(request));
   }
   catch(SomeException ex)
   {
       // at least try to log it ...
   }
});