public static NameValueCollection DecryptQueryString(string queryString)
    {
        if (queryString.Length != 0)
        {
            //Decode the string
            string decodedQueryString = HttpUtility.UrlDecode(queryString);
            //Decrypt the string
            string QUERY_STRING_DELIMITER;
            string decryptedQueryString = StringHelpers.Decrypt(decodedQueryString);
            //Now split the string based on each parameter
           string[] actionQueryString = decryptedQueryString.Split(new char[] {QUERY_STRING_DELIMITER}); //(QUERY_STRING_DELIMITER);
            NameValueCollection newQueryString = new NameValueCollection();
            //loop around for each name value pair.
            for (int index = 0; index < actionQueryString.Length; index++)
            {
                string[] queryStringItem = actionQueryString[index].Split(new char[] { '=' });
                newQueryString.Add(queryStringItem[0], queryStringItem[1]);
            }
            return newQueryString;
        }
        else
        {
            //No query string was passed in.
            return null;
        }
    }
    public static string EncryptQueryString(NameValueCollection queryString)
    {
        //create a string for each value in the query string passed in.
        string tempQueryString = "";
        for (int index = 0; index < queryString.Count; index++)
        {
            tempQueryString += queryString.GetKey(index) + "=" + queryString[index];
            if (index != queryString.Count - 1)
            {
                tempQueryString += QUERY_STRING_DELIMITER;
            }
        }
        return EncryptQueryString(tempQueryString);
    }