Filter ≈ Array.FindAllHe also has a follow up in C# 3.0 using lambda functions. Found courtesy of Oren.
() and List .FindAll(). Map ≈ Array.ConvertAll () and List .ConvertAll ().
Great article from Dustin Campbell on implementing Map, Filter, and Reduce from the functional programming world using C# 2.0. His explanations of the concepts are great, although he notes that there are limited implementations of Map and Filter already in .NET (but not Reduce):