f# byte[] -> hex -> string conversion

let ByteToHex bytes =
    bytes
    |> Array.map (fun (x : byte) -> String.Format("{0:X2}", x))

let ConcatArray stringArray = String.Join(null, (ByteToHex  stringArray))

let ByteToHex bytes =
    bytes
    |> Array.map (fun (x : byte) -> System.String.Format("{0:X2}", x))
    |> String.concat System.String.Empty

val ksprintf : (string -> 'd) -> StringFormat<'a,'d> -> 'a
    sprintf, but call the given 'final' function to generate the result.

StringBuilder sb = new StringBuilder();
        foreach (byte b in raw) {
            sb.Append(b.ToString("x2"));
        }
        return sb.ToString()