>>And I really wish that C# would grow up a little in this regard, as modern programming languages need immutable collections as well, with a nice API to go along with it May I suggest the Immutable Collection library from Microsoft? http://msdn.microsoft.com/en-us/library/dn385366(v=vs.110).a...

Admittedly not part of the core library, but installing a NuGet package is pretty darn easy.

>>This is what happens when you pass judgement unto things you don't understand ;)

[edit: Guess I should've refreshed the page to see the prior response before writing this. Apologies.]