Parallel.ForEach() vs. foreach(IEnumerable.AsParallel())

Question

Erg, I\'m trying to find these two methods in the BCL using Reflector, but can\'t locate them. What\'s the difference between these two snippets?

A:

Answer 1

The difference is, B isn't parallel. The only thing AsParallel() does is that it wraps around a IEnumerable, so that when you use LINQ methods, their parallel variants are used. The wrapper's GetEnumerator() (which is used behind the scenes in the foreach) even returns the result of the original collection's GetEnumerator().

BTW, if you want to look at the methods in Reflector, AsParallel() is in the System.Linq.ParallelEnumerable class in the System.Core assembly. Parallel.ForEach() is in the mscorlib assembly (namespace System.Threading.Tasks).