F# basics: turning NameValueCollection into nice string

Question

Learning F# while trying to do something useful at the same time, so this is kind of basic question:

I have req, which is a HttpListenerRequest, which has QueryString property, with type System.Collections.Specialized.NameValueCollection. So, for sake of clarity let's say, I have

let queryString = req.QueryString

Now I want to produce nice string (not printf to console) from contents of that, but queryString.ToString() is not overriden apparently, so it just gives string "System.Collections.Specialized.NameValueCollection".

So, what's the F# one-liner to get a nice string out of that, like "key1=value1\nkey2=value2\n..."?

Answer 1

nvc.AllKeys
|> Seq.map (fun key -> sprintf "%s=%s" key nvc.[key])
|> String.concat "\n"

Answer 2

Something like this ought to work:

let nvcToString (nvc:System.Collections.Specialized.NameValueCollection) =
    System.String.Join("\n", 
                       seq { for key in nvc -> sprintf "%s=%s" key nvc.[key] })