An interesting feature in .NET 4.5 is the ability to process collection in parallel. Along with the async/await feature, you can really improve the performance of your application with a few simple steps. Whereas both components are documented really well, I thought this would be a walk in the park. However, you should pay attention when you want to return a collection that was modified in the parallel block. If you don’t, you might be missing a few items in the list.