public static string UrlEncode(string str)

        {

            StringBuilder sb = new StringBuilder();

            byte[] byStr = System.Text.Encoding.UTF8.GetBytes(str); //默认是System.Text.Encoding.Default.GetBytes(str)

            for (int i = 0; i < byStr.Length; i++)

            {

                sb.Append(@"%" + Convert.ToString(byStr[i], 16));

            }

           

            return (sb.ToString());

        }