Is it possible to use C# LINQ from Mathematica using .NET/Link?

Question

Using Mathematica's .NET/Link (NETLink`) package, is it possible to call out to .NET's LINQ facilities for list manipulation and other operations?

Answer 1

Yes, it is, but it's cumbersome (at least as of Mathematica 8). The hardest part is that you have to manually do a lot of the juggling required to work with .NET generics and extension methods.

For example, let's translate a straightforward solution to Project Euler's Problem #1 ("Add all the natural numbers below one thousand that are multiples of 3 or 5.") from LINQ:

Enumerable.Range(1, 999)
.Where(x => x % 5 == 0 || x % 3 == 0)
.Sum();

To .NET/Link:

(* Load stuff. *)
<< NETLink`;
InstallNET[];
LoadNETType["System.Linq.Enumerable"];

(* Create our enumerable list of numbers. *)
numbers = Enumerable`Range[1,999];

(* Create the filter that we're going to apply. *)
enumerableType = GetTypeObject[LoadNETType["System.Linq.Enumerable"]];
meths = enumerableType@GetMethods[];
whereMethod = First[Select[meths, #@Name == "Where" && Length[#@GetParameters[]] == 2&]];
intTypeParams = {GetTypeObject[LoadNETType["System.Int32"]]};
intWhereMethod = whereMethod@MakeGenericMethod[intTypeParams];
divisibleByThreeOrFive[n_] := Or[Mod[n, 3] == 0, Mod[n, 5] == 0];
whereCondition = NETNewDelegate["System.Func`2[System.Int32,System.Boolean]", divisibleByThreeOrFive];

(* Apply the filter to the list. *)
filteredNumbers = intWhereMethod@Invoke[Null, {numbers, whereCondition}];

(* Pump all the results through the filter and Sum. *)
Enumerable`Sum[filteredNumbers]