Generate QueryString Parameters

        protected static string GenerateQueryStringParameters(HttpRequest request, params string[] queryStringKeys)
        {
            StringBuilder queryString = new StringBuilder(64);
            foreach (string key in queryStringKeys)
            {
                if (request.QueryString[key] != null)
                {
                    if (queryString.Length > 0)
                    {
                        queryString.Append("&");
                    }

                    queryString.Append(key).Append("=").Append(request.QueryString[key]);
                }
            }

            return queryString.ToString();
        }

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