C#写爬虫，版本V2.1

　　这次是对2.0的小修补，2.0交互几乎没有，这次添加了进度条，和文本框，同时由于取得的链接主要会出现错误是：webResponse错误。

针对这种情况，设置了

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

截取错误信息，这里我们不处理，后续直接判定statecode属性来决定是否还要执行下面的程序。

另外一点变化就是以前是通过将所获取的网页存到文本中去，这次

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();

将它全放入了string中。

最后一点是去掉了DownloadPage这个方法，如上，它的功能可以放入按钮的单击事件中实现，没有必要把一件事做两遍。

下面是前台页面：

后台代码：

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 百度图片爬虫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); //新建正则模式
            MatchCollection m = r.Matches(html); //获得匹配结果
            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(); //提取出结果
                    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("下载结束");
                            this.textBox2.Text += sb.ToString();
                        }));
                    }, fun);
                }
            }
        }
        private static bool isValiable(string url)
        {
            if (url.Contains(".jpg") || url.Contains(".gif") || url.Contains(".png"))
            {
                return true; //得到一些图片之类的资源
            }
            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;
                //设置连接超时时间
                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))//判断如果是图片，就将其存储到数据库中。
                    {
                        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("图片下载开始" + Environment.NewLine);
                            this.textBox2.Text += sb1.ToString();
                        }));
                    }
                }
            }
        }

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