FSharpQueryJoinExample.fs

type Claim = { Name: string; Value: string }

type Mapping = { Group: string; Roles: string list }

let mapping = [
    { Group = "aaa"; Roles = [ "Admin" ] }
    { Group = "ccc"; Roles = [ "King" ] }
    { Group = "uuu"; Roles = [ "User" ] }
]

let groups = [ "aaa"; "bbb"; "ccc" ]

let joinedList =
    query {
        for group in groups do
        join mapping in mapping on (group.ToUpperInvariant() = mapping.Group.ToUpperInvariant())
        select mapping
    } |> Seq.toList

// The same query in C# LINQ:
// var joined =
// (
//   from adGroup in groups
//   join mappingRecord in mapping
//     on adGroup.ToUpperInvariant() equals mappingRecord.Group.ToUpperInvariant()
//   select mappingRecord
// ).ToList();