C#寫爬蟲，版本V2.1

　　這次是對2.0的小修補，2.0交互幾乎沒有，這次添加了進度條，和文本框，同時由於取得的鏈接主要會出現錯誤是：webResponse錯誤。

針對這種情況，設置了

 try
                {
                    webResponse = (HttpWebResponse)webRequest.GetResponse();
                }
                catch(WebException ex)
                {
                    webResponse = (HttpWebResponse)ex.Response;
                }

截取錯誤信息，這裡我們不處理，後續直接判定statecode屬性來決定是否還要執行下麵的程式。

另外一點變化就是以前是通過將所獲取的網頁存到文本中去，這次

WebRequest myRequest = WebRequest.Create("http://image.baidu.com/search/index?tn=baiduimage&ipn=r&ct=201326592&cl=2&lm=-1&st=-1&fm=result&fr=&sf=1&fmq=1466307565574_R&pv=&ic=0&nc=1&z=&se=1&showtab=0&fb=0&width=&height=&face=0&istype=2&ie=utf-8&word=" + Uri.EscapeDataString(keyWord));
            HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();
            if (myResponse.StatusCode == HttpStatusCode.OK)
            {
                Stream strm = myResponse.GetResponseStream();
                StreamReader sr = new StreamReader(strm);
                string line = sr.ReadToEnd();

將它全放入了string中。

最後一點是去掉了DownloadPage這個方法，如上，它的功能可以放入按鈕的單擊事件中實現，沒有必要把一件事做兩遍。

下麵是前臺頁面：

後臺代碼：

using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace 百度圖片爬蟲V2._1
{
    public partial class Form1 : Form
    {
        public delegate void AsynFunction(string s,int i);
        public Form1()
        {
            InitializeComponent();
        }
        private static string[] getLinks(string html, out int counts)
        {
            const string pattern = @"http://([\w-]+\.)+[\w-]+(/[\w- ./?%&=]*)?";
            Regex r = new Regex(pattern, RegexOptions.IgnoreCase); //新建正則模式
            MatchCollection m = r.Matches(html); //獲得匹配結果
            string[] links = new string[m.Count];
            int count = 0;
            for (int i = 0; i < m.Count; i++)
            {
                if (isValiable(m[i].ToString()))
                {
                    links[count] = m[i].ToString(); //提取出結果
                    count++;
                }

            }
            counts = count;
            return links;
        }
        private void button1_Click(object sender, EventArgs e)
        {
            string keyWord = this.textBox1.Text;
            WebRequest myRequest = WebRequest.Create("http://image.baidu.com/search/index?tn=baiduimage&ipn=r&ct=201326592&cl=2&lm=-1&st=-1&fm=result&fr=&sf=1&fmq=1466307565574_R&pv=&ic=0&nc=1&z=&se=1&showtab=0&fb=0&width=&height=&face=0&istype=2&ie=utf-8&word=" + Uri.EscapeDataString(keyWord));
            HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();
            if (myResponse.StatusCode == HttpStatusCode.OK)
            {
                Stream strm = myResponse.GetResponseStream();
                StreamReader sr = new StreamReader(strm);
                string line = sr.ReadToEnd();
                int counts = 0;
                string[] str = getLinks(line, out counts);
                this.progressBar1.Maximum = counts;
                for (int i = 0; i < counts; i++)
                {
                    AsynFunction fun = new AsynFunction(savePicture);
                    fun.BeginInvoke(str[i],i, ar => {
                        fun.EndInvoke(ar);
                        this.progressBar1.BeginInvoke(new Action(() =>
                        {
                            this.progressBar1.Value =progressBar1.Maximum;
                        }));
                        this.textBox2.BeginInvoke(new Action(() =>
                        {
                            StringBuilder sb=new StringBuilder();
                            sb.Append(Environment.NewLine);
                          //  sb.Append(str[i].ToString());
                            sb.Append("下載結束");
                            this.textBox2.Text += sb.ToString();
                        }));
                    }, fun);
                }
            }
        }
        private static bool isValiable(string url)
        {
            if (url.Contains(".jpg") || url.Contains(".gif") || url.Contains(".png"))
            {
                return true; //得到一些圖片之類的資源
            }
            return false;
        }
        public void savePicture(string path,int i)
        {
            if (path != "" && path != null)
            {
                DataClasses1DataContext db = new DataClasses1DataContext();
                Uri url = new Uri(path);
                HttpWebRequest webRequest = (HttpWebRequest)HttpWebRequest.Create(url);
                webRequest.Referer = "http://image.baidu.com";
                webRequest.Timeout = 30000;
                //設置連接超時時間 
                webRequest.AllowAutoRedirect = true;
                webRequest.Headers.Set("Pragma", "no-cache");
                webRequest.UserAgent = "Mozilla-Firefox-Spider(Wenanry)";
                HttpWebResponse webResponse;
                try
                {
                    webResponse = (HttpWebResponse)webRequest.GetResponse();
                }
                catch(WebException ex)
                {
                    webResponse = (HttpWebResponse)ex.Response;
                }
             
                if(webResponse!=null&&webResponse.StatusCode==HttpStatusCode.OK)
                {

                    if (isValiable(path))//判斷如果是圖片，就將其存儲到資料庫中。
                    {
                        Bitmap myImage = new Bitmap(webResponse.GetResponseStream());

                        MemoryStream ms = new MemoryStream();
                        myImage.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
                        var p = new pictureUrl
                        {
                            pictureUrl1 = ms.ToArray()
                        };
                        db.pictureUrl.InsertOnSubmit(p);
                        db.SubmitChanges();
                        this.progressBar1.BeginInvoke(new Action(() =>
                        {
                            this.progressBar1.Value = i;
                        }));
                        this.textBox2.BeginInvoke(new Action(() =>
                        {
                            StringBuilder sb1 = new StringBuilder();
                            sb1.Append(path);
                            sb1.Append("圖片下載開始" + Environment.NewLine);
                            this.textBox2.Text += sb1.ToString();
                        }));                     
                    }
                }
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}