WebResponse 取出全国省市区的邮编

WebResponse用法（根据省市区地址查询其邮编）：

class Program
    {
        static string url { get; set; }
        static void Main(string[] args)
        {
            StringBuilder sb = new StringBuilder();
            try
            {
                SqlConnection conn = new SqlConnection("自己的数据库连接语句");
                SqlDataAdapter da = new SqlDataAdapter("查询语句", conn);
                DataSet ds = new DataSet();
                Random rd = new Random();
                da.Fill(ds);
                url = "http://opendata.baidu.com/post/s?wd={0}&rn=20";//请求地址
                for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
                {
                    var row = ds.Tables[0].Rows[i];
                    string keyworder = row["ProvinceName"] + " " + row["CityName"] + " " + row["DistrictName"];
                    sb.Append(GetZipCodeSql(keyworder, row["SysNo"].ToString()));

                    Thread.Sleep(rd.Next(0, 1000));//延时
                    if (i != 0 && i % 100 == 0)
                    {
                        WriteTxt(sb.ToString());

                        sb.Clear();
                    }
                    else if (i == ds.Tables[0].Rows.Count - 1)
                    {
                        WriteTxt(sb.ToString());

                        sb.Clear();
                    }
                }
            }
            catch (Exception ex)
            {
                System.Console.WriteLine(ex.Message);
            }
        }
        private static void WriteTxt(string text)
        {
            StreamWriter sw = File.AppendText("D:\\3.txt");//保存输出的位置
            sw.Write(text);
            sw.Close();
        }　　　　//得到邮编
        private static string GetZipCodeSql(string keyworder, string sysNo)
        {
            StringBuilder sb = new StringBuilder();
            try
            {
                HttpWebRequest httpweb = (HttpWebRequest)WebRequest.Create(
                    new Uri(string.Format(url, HttpUtility.UrlEncode(keyworder, System.Text.Encoding.GetEncoding("GBK"))))
                        );
                WebResponse respon = httpweb.GetResponse();
                StreamReader reader = new StreamReader(respon.GetResponseStream(), Encoding.GetEncoding("GBK"));
                string html = reader.ReadToEnd();
                int statrtIndex = 0;
                int end = 0;
                string code = "";
                statrtIndex = html.IndexOf("<ul><!-- baidu-tc begin -->");
                if (statrtIndex > 0)
                {
                    end = html.IndexOf("</a>", statrtIndex);
                    statrtIndex = html.LastIndexOf("</em>", end);
                    code = Regex.Replace(html.Substring(end - 22, 22), @"[^0-9]", "");
                    //code = html.Substring(end - 6, 6);
                    sb.AppendFormat("UPDATE area SET ZipCode ={0} WHERE SysNo={1};\r\n", code, sysNo);
                }
                respon.Close();
            }
            catch (Exception)
            {
                url = "http://opendata.baidu.com/post/s?wd={0}&p=mini&rn=20";
                GetZipCodeSql(keyworder, sysNo);
            }

            return sb.ToString();
        }
    }