I get that you can call across to another language that has more functional features. But that's not the same as having little bits of it right there. e.g. when you want to find the latest item in a list, instead of a loop, you do:

   return purchaseList.OrderBy(pur => pur.Date).FirstOrDefault();

and carry on. It's great. You don't tend to have that fine granularity when working across languages.

I don't know if you missed F# or not, but if you want a fully functional language in the ML / Ocaml lineage on .Net, you can write some code in that and interoperate.