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

Apparently there may be a solution as indicated in by using a combination of groupValBy and AnonymousObject<_,_> from the Linq RuntimeHelpers.

ex.

query {
    for d in context.table do
    let key = AnonymousObject<_,_>(d.col1,d.col2)
    groupValBy d key into g
    select (g.Key)
    }