[olmo]

It's true, but 95% of the cases you get much better results by using the right data structures (dictionaries) instead of transforming queries to loops. Still is a very cool thing, hopefully is standardized into Roslyn

[jsingleton]

Using the best structure is a good idea but simple LINQ is very readable if performance isn't a big concern.

BTW I cover this in my recent book: https://www.packtpub.com/mapt/book/Application%20Development...

You could try code samples and benchmarks: https://github.com/PacktPublishing/ASP.NET-Core-1.0-High-Per...

[platz]

How would the provided example be better realized as a dictionary?

[SideburnsOfDoom]

All true, but the example is a demo that doesn't do anything useful, and not typical code.