Updates a querystring parameter with a new value

Update Querystring Parameter

 /// <summary>
        /// Updates a querystring parameter with a new value
        /// </summary>
        /// <param name="req">The HTTPRequest object</param>
        /// <param name="parameterName">The parameter name to update</param>
        /// <param name="parameterValue">The new value for the parameter</param>
        /// <returns></returns>
        public static string UpdateQueryString(HttpRequest req, string parameterName, string parameterValue)
        {

            var nameValues = HttpUtility.ParseQueryString(req.QueryString.ToString());
            nameValues[parameterName] = parameterValue;
            string url = req.Url.AbsolutePath;
            string updatedQueryString = "?" + nameValues.ToString();
            return (url + updatedQueryString);

        }