WebRequest實現讀取天氣預報信息

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.Net;
using System.IO;
namespace WebApplication1
{
 /// <summary>
 /// Summary description for WebForm1.
 /// </summary>
 public class WebForm1 : System.Web.UI.Page
 {
  protected System.Web.UI.WebControls.Label l_date;
  protected System.Web.UI.WebControls.Label l_city;
  protected System.Web.UI.WebControls.Label l_wea;
  protected System.Web.UI.WebControls.Label l_sky;
  protected System.Web.UI.WebControls.Label l_w1;
  protected System.Web.UI.WebControls.Label l_w2;
  protected System.Web.UI.WebControls.Button Button1;
  protected System.Web.UI.WebControls.Label Label1;
  protected System.Web.UI.WebControls.Label l_w3;
  protected System.Web.UI.WebControls.Label l_w4;
  protected System.Web.UI.WebControls.DropDownList ddlcity;
 
  private void Page_Load(object sender, System.EventArgs e)
  {
   if (!Page.IsPostBack)
   {
    writeWeatherInfo(ddlcity.SelectedValue);
    writeWeather(ddlcity.SelectedValue);
   }
  } 

  #region getWeatherByCity 通過城市過慮
  public string getWeatherByCity(string city)
  {
   string temp = null;
   try
   {
    string strURL = "http://weather.news.sina.com.cn/cgi-bin/figureWeather/search.cgi";
    HttpWebRequest request= (HttpWebRequest)WebRequest.Create(strURL);//使用 WebRequest.Create 方法初始化 HttpWebRequest 的一個新實例。如果 URI 的方案是 http:// 或 https://，則 Create 將返回 HttpWebRequest 實例。
    request.Method="POST"; //Post請求方式
    request.ContentType="application/x-www-form-urlencoded"; //內容類型
    string paraUrlCoded = System.Web.HttpUtility.UrlEncode("city"); //參數經過URL編碼
    paraUrlCoded = paraUrlCoded + "=" + System.Web.HttpUtility.UrlEncode(city, System.Text.Encoding.GetEncoding("GB2312"));
    byte[] payload = System.Text.Encoding.GetEncoding("GB2312").GetBytes(paraUrlCoded); //將URL編碼後的字符串轉化爲字節
    request.ContentLength = payload.Length; //設置請求的ContentLength
    Stream writer = request.GetRequestStream(); //獲得請求流
    writer.Write(payload,0,payload.Length); //將請求參數寫入流
    writer.Close(); //關閉請求流
    HttpWebResponse response = (HttpWebResponse)request.GetResponse(); //獲得響應流
    Stream s= response.GetResponseStream();
    StreamReader objReader = new StreamReader(s,System.Text.Encoding.GetEncoding("GB2312"));
    string HTML = "";
    string sLine = "";
    int i = 0;
    while (sLine!=null)
    {
     i++;
     sLine = objReader.ReadLine();
     if (sLine!=null)
      HTML += sLine;
    }
    HTML = HTML.Replace("&lt;","<");
    HTML = HTML.Replace("&gt;",">");
    int start,stop;
    //start = HTML.IndexOf("<img src=/"http://image2.sina.com.cn/dy/weather/images/figure/",0,HTML.Length);
    start = HTML.IndexOf("<table border=0 cellpadding=0 cellspacing=0 style=/"margin:5px;/">",0,HTML.Length);
    stop = HTML.IndexOf("<td background=http://image2.sina.com.cn/dy/weather/images",start);
    temp = HTML.Substring(start, stop - start);
   }
   catch (Exception x)
   {
   }
   return temp;
  }

  #endregion

  #region writeWeatherInfo 顯示處理後的信息
  private void writeWeatherInfo(string city)
  {
   int start,stop;
   string weather1,weather2,wea;
   string wea_city = getWeatherByCity(city);

   wea_city = wea_city.Replace(" ","");

   start = wea_city.IndexOf("<b>",0,wea_city.Length);
   stop = wea_city.IndexOf("</b>", start);
   weather1 = wea_city.Substring(start, stop-start).Trim() + "          ";
   weather1 = weather1.Substring(3,8).Trim();
  
   start = wea_city.IndexOf("<tdstyle=/"font-size:40px;font-family:TimesNewRoman;font-weight:bold;/">",0,wea_city.Length);
   stop = wea_city.IndexOf("℃",start) + 40;
   weather2 = wea_city.Substring(start, stop-start);
   weather2 = weather2.Substring(stop-start-42,40).Trim();
   weather2 = weather2.Replace("/t","");

   start = wea_city.IndexOf("<fontcolor=#183888><b>", 0, wea_city.Length);
   stop = wea_city.IndexOf("</b></font>",start);
   wea = wea_city.Substring(start,stop-start);
   wea = wea.Substring(22,wea.Length-22) + "kbrk";
   wea = wea.Replace("/t", "");
   wea = wea.Replace(">", "k");
   wea = wea.Replace("<", "k");
   wea = wea.Replace("kbrk", "k");
   string [] wall = null;
   char[] seperator = {'k'};
   wall = wea.Split(seperator);

   
   l_city.Text = "[城市]：" + city;//城市
   l_wea.Text = "[天氣]：" + weather1;//天氣
   l_sky.Text = "[溫度]：" + weather2;//溫度
   
   l_date.Text = wall[0];//日期
   l_w1.Text = wall[1];//風向
   l_w2.Text = wall[2];//風力
   l_w3.Text = wall[3]; //空氣質量
   l_w4.Text = wall[4]; //紫外線強度
  }
 
  #endregion

  #region writeWeather 直接顯示讀取到的信息
  private void writeWeather(string city)
  {
   string wea_city = getWeatherByCity(city);
   Response.Write(wea_city);
  }
  #endregion
 
  #region Button1_Click
  private void Button1_Click(object sender, System.EventArgs e)
  {
   writeWeatherInfo(ddlcity.SelectedValue);
   writeWeather(ddlcity.SelectedValue);
  }
  #endregion

  #region Web Form Designer generated code
  override protected void OnInit(EventArgs e)
  {
   //
   // CODEGEN: This call is required by the ASP.NET Web Form Designer.
   //
   InitializeComponent();
   base.OnInit(e);
  }
  
  /// <summary>
  /// Required method for Designer support - do not modify
  /// the contents of this method with the code editor.
  /// </summary>
  private void InitializeComponent()
  {   
   this.Button1.Click += new System.EventHandler(this.Button1_Click);
   this.Load += new System.EventHandler(this.Page_Load);

  }
  #endregion

 }
}

源碼：http://singlepine.cnblogs.com/Files/singlepine/Weather.rar