PurelyFunctionalDataStructures is a project mainly written in C#, it's free.
an implementations of some of the data structures found in Chris Okasakis book "Purely Functional Data Structures" in the C# language.
This is an implementation of some of the datastructures described in Chris Okasaki's Book "Purely Functional Data Structures" all the implmentations are in C# and try to implement the described algorithms as faithfully as possible while still implementing in an object oriented manner.