groupby multiple columns in a F# 3.0 query

Question

Just trying out F# 3.0 and hit a bit of a wall when it comes to grouping by multiple columns. The obvious thing to try was

query {
    for d in context.table         


        

Answer 1

open Microsoft.FSharp.Linq.RuntimeHelpers
open System.Linq

query {
    for d in context.table do
    let t = MutableTuple<_,_>(Item1=d.col1,Item2=d.col2)
    groupValBy d t into g
    select (g.Key,g.Count())
    }