url 编码方法

private string UrlEncode(string str,string encoding)
        {
            StringBuilder sb = new StringBuilder();
            byte[] byStr = System.Text.Encoding.GetEncoding(encoding).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());
        }