LINQ practice exercises or puzzles?

Question

I'm still trying to learn LINQ, though it's going more smoothly now that I've started to use it daily at work. I still don't feel good at it, though. Does anyone have any challenging practice exercises or puzzles I can use as a code-kata to improve my skills?

I'll leave this as community wiki, so maybe it can grow to a community list.

Answer 1

101 Linq Samples is a good one for refference. Not a puzzle though

Answer 2

I know the 1st 2 questions at Project Euler is 'LINQ' friendly, I never did any more, but it should be fun either way :)

Answer 3

If you have not discovered http://www.linqpad.net/ it lets you practice linq in a lightweight way, as well as having some inbuilt examples from C# 3.0 in a nutshell book.

Answer 4

I've been finding "foreach's" in existing code and attempting to linq'ify them. Many times things have been different enough for me to learn new concepts or at least if they're similar I get to feel more confident that my Linq skills are getting better.

Answer 5

Puzzle:

Do a full outer join in LINQ.