Facebook.FacebookClient.BuildHttpQuery C# (CSharp) Method

        private static string BuildHttpQuery(object parameter, Func<string, string> encode)
        {
            if (parameter == null)
                return "null";
            if (parameter is string)
                return (string)parameter;
            if (parameter is bool)
                return (bool)parameter ? "true" : "false";

            if (parameter is int || parameter is long ||
                parameter is float || parameter is double || parameter is decimal ||
                parameter is byte || parameter is sbyte ||
                parameter is short || parameter is ushort ||
                parameter is uint || parameter is ulong)
                return parameter.ToString();

            if (parameter is Uri)
                return parameter.ToString();

            // todo: IEnumerable<KeyValuePair<T1,T2>> and IEnumerable<Tuple<T1, T2>>

            var sb = new StringBuilder();
            if (parameter is IEnumerable<KeyValuePair<string, object>>)
            {
                foreach (var kvp in (IEnumerable<KeyValuePair<string, object>>)parameter)
                    sb.AppendFormat("{0}={1}&", encode(kvp.Key), encode(BuildHttpQuery(kvp.Value, encode)));
            }
            else if (parameter is IEnumerable<KeyValuePair<string, string>>)
            {
                foreach (var kvp in (IEnumerable<KeyValuePair<string, string>>)parameter)
                    sb.AppendFormat("{0}={1}&", encode(kvp.Key), encode(kvp.Value));
            }
            else if (parameter is IEnumerable)
            {
                foreach (var obj in (IEnumerable)parameter)
                    sb.AppendFormat("{0},", encode(BuildHttpQuery(obj, encode)));
            }
            else if (parameter is DateTime)
            {
                return DateTimeConvertor.ToIso8601FormattedDateTime((DateTime)parameter);
            }
            else
            {
                IDictionary<string, FacebookMediaObject> mediaObjects;
                IDictionary<string, FacebookMediaStream> mediaStreams;
                var dict = ToDictionary(parameter, out mediaObjects, out mediaStreams);
                if (mediaObjects.Count > 0 || mediaStreams.Count > 0)
                    throw new InvalidOperationException("Parameter can contain attachements (FacebookMediaObject/FacebookMediaStream) only in the top most level.");
                return BuildHttpQuery(dict, encode);
            }

            if (sb.Length > 0)
                sb.Length--;

            return sb.ToString();
        }