Convert discriminated union values to and from strings

unionAsString.fsx

open Microsoft.FSharp.Reflection

let toString (x: 'T) = 
    match FSharpValue.GetUnionFields(x, typeof<'T>) with
    | case, _ -> case.Name

let fromString<'T> (s: string) =
    match FSharpType.GetUnionCases typeof<'T> |> Array.filter (fun case -> case.Name = s) with
    | [|case|] -> Some(FSharpValue.MakeUnion(case, [||]) :?> 'T)
    | _        -> None