C#获取网页信息核心方法（入门一）

目录：信息采集入门系列目录

 下面记录的是我自己整理的C#请求页面核心类，主要有如下几个方法

1.HttpWebRequest Get请求获得页面html

2.HttpWebRequest Post请求获得页面html

3.模拟登录获得cookie内容

4.模拟登录获得cookie字符串

5.代理的设置

6.利用webbrowser 获取js生成的页面

7.为webbrowser设置cookie，模拟登录

8.使用demo

HttpWebRequest Get请求获得页面html

注意点：以前抓取觉得很慢，最后发现是代理的问题，没有代理就设置为null,这样就不用每次去找代理，影响执行效率，还有一些参数可以自习设置，比如模拟浏览器等。

        /// <summary>
        /// get请求获得页面的html
        /// </summary>
        /// <param name="url">需要获取的url</param>
        /// <param name="proxy">代理，没有设置为null,不然每次去读代理造成请求很慢</param>
        /// <param name="cookie">该网站所需要的cookie</param>
        /// <param name="timeout">超时时间</param>
        /// <returns>页面请求后的html</returns>
        public static string Crawl(string url, WebProxy proxy, CookieContainer cookie, int timeout = 10000)
        {
            string result = string.Empty;
            HttpWebRequest request = null;
            WebResponse response = null;
            StreamReader streamReader = null;
            try
            {
                request = (HttpWebRequest)HttpWebRequest.Create(url);
                request.Proxy = proxy;
                request.Timeout = timeout;
                request.AllowAutoRedirect = true;
                request.CookieContainer = cookie;
                response = (HttpWebResponse)request.GetResponse();
                streamReader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
                result = streamReader.ReadToEnd();

            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (request != null)
                {
                    request.Abort();
                }
                if (response != null)
                {
                    response.Close();
                }
                if (streamReader != null)
                {
                    streamReader.Dispose();
                }
            }

            return result;
        }

HttpWebRequest Post请求获得页面html

        /// <summary>
        /// post请求获得页面
        /// </summary>
        /// <param name="url">需要获取的url</param>
        /// <param name="postdata">post的数据字符串，如id=1&name=test</param>
        /// <param name="proxy">代理</param>
        /// <param name="cookie">coolie</param>
        /// <param name="timeout">超时</param>
        /// <returns></returns>
        public static string Crawl(string url, string postdata,WebProxy proxy, CookieContainer cookie, int timeout = 10000)
        {
            string result = string.Empty;
            HttpWebRequest request = null;
            WebResponse response = null;
            StreamReader streamReader = null;
            try
            {
                request = (HttpWebRequest)HttpWebRequest.Create(url);
                request.Proxy = proxy;
                request.Timeout = timeout;
                request.AllowAutoRedirect = true;
                request.CookieContainer = cookie;

                byte[] bs = Encoding.ASCII.GetBytes(postdata);
                string responseData = String.Empty;
                request.Method = "POST";
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = bs.Length;
                using (Stream reqStream = request.GetRequestStream())
                {
                    reqStream.Write(bs, 0, bs.Length);
                    reqStream.Close();
                }
                response = (HttpWebResponse)request.GetResponse();
                streamReader = new StreamReader(response.GetResponseStream(), Encoding.UTF8);
                result = streamReader.ReadToEnd();

            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (request != null)
                {
                    request.Abort();
                }
                if (response != null)
                {
                    response.Close();
                }
                if (streamReader != null)
                {
                    streamReader.Dispose();
                }
            }

            return result;
        }

模拟登录获得cookie内容

先找到登录的页面，分析登录页面的post参数和链接，获得cookie后可以直接传到上面的方法

        /// <summary>
        ///根据模拟请求页面获得cookie
        /// </summary>
        /// <param name="url">模拟的url</param>
        /// <returns>cookie</returns>
        public static CookieContainer GetCookie(string url, WebProxy proxy, int timeout = 10000)
        {
            HttpWebRequest request = null;
            HttpWebResponse response = null;
            try
            {
                CookieContainer cc = new CookieContainer();
                request = (HttpWebRequest)HttpWebRequest.Create(url);
                request.Proxy = proxy;
                request.Timeout = timeout;
                request.AllowAutoRedirect = true;
                request.CookieContainer = cc;
                response = (HttpWebResponse)request.GetResponse();
                response.Cookies = request.CookieContainer.GetCookies(request.RequestUri);
                return cc;
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (request != null)
                {
                    request.Abort();
                }
                if (response != null)
                {
                    response.Close();
                }
            }

        }

模拟登录获得cookie字符串

        /// <summary>
        /// 获得cookie字符串，webbrowser可以使用
        /// </summary>
        /// <param name="url"></param>
        /// <param name="proxy"></param>
        /// <param name="timeout"></param>
        /// <returns></returns>
        public static string GetCookieString(string url, WebProxy proxy, int timeout = 10000)
        {
            HttpWebRequest request = null;
            HttpWebResponse response = null;
            try
            {
                CookieContainer cc = new CookieContainer();
                request = (HttpWebRequest)HttpWebRequest.Create(url);
                request.Proxy = proxy;
                request.Timeout = timeout;
                request.AllowAutoRedirect = true;
                request.CookieContainer = cc;
                response = (HttpWebResponse)request.GetResponse();
                response.Cookies = request.CookieContainer.GetCookies(request.RequestUri);
                string strcrook = request.CookieContainer.GetCookieHeader(request.RequestUri);
                return strcrook;

            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                if (request != null)
                {
                    request.Abort();
                }
                if (response != null)
                {
                    response.Close();
                }
            }
        }

代理的设置

       /// <summary>
        /// 创建代理
        /// </summary>
        /// <param name="port">代理端口</param>
        /// <param name="user">用户名</param>
        /// <param name="password">密码</param>
        /// <returns></returns>
        public static WebProxy CreatePorxy(string port, string user, string password)
        {
            WebProxy proxy = new WebProxy(); 
            proxy.Address = new Uri(port); 
            proxy.Credentials = new NetworkCredential(user, password); 
            return proxy;
        }

利用webbrowser 获取js生成的页面

说明：由于不知道页面什么时候执行完成，这里是等待5s，默认执行完成，效率有待提高。

另外执行需要线程安全添加[STAThread]

        /// <summary>
        /// 抓取js生成的页面
        /// </summary>
        /// <param name="url"></param>
        /// <returns></returns>
        public static string CrawlDynamic(string url)
        {
            WebBrowser browser = new WebBrowser();

            browser.ScriptErrorsSuppressed = true;

            browser.Navigate(url);

            //先要等待加载完毕
            while (browser.ReadyState != WebBrowserReadyState.Complete)
            {
                Application.DoEvents();
            }

            System.Timers.Timer timer = new System.Timers.Timer();

            var isComplete = false;

            timer.Elapsed += new System.Timers.ElapsedEventHandler((sender, e) =>
            {
                //加载完毕
                isComplete = true;

                timer.Stop();
            });

            timer.Interval = 1000 * 5;

            timer.Start();

            //继续等待 5s，等待js加载完
            while (!isComplete)
                Application.DoEvents();

            var htmldocument = browser.Document;
            return htmldocument.ActiveElement.InnerHtml;
        }

为webbrowser设置cookie，模拟登录

 刚开始始终不成功以为这个方法不能用，后面发现原来是doain设置有问题，我的例子是www.aa.xxx.com,设置的为http://xx.com可以使用，这个地方可能需要根据自己的情况来选择域名。

        [DllImport("wininet.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public static extern bool InternetSetCookie(string lpszUrlName, string lbszCookieName, string lpszCookieData);

        /// <summary>
        /// 为webbrowser设置cookie
        /// </summary>
        /// <param name="cookieStr">cookie字符串，可以从上面方法获得</param>
        /// <param name="domain">需要设置的域名</param>
        public static void SetCookie(string cookieStr,string domain)
        {
            foreach (string c in cookieStr.Split(';'))
            {
                string[] item = c.Split('=');
                if (item.Length == 2)
                {
                    string name = item[0];
                    string value = item[1];
                    InternetSetCookie(domain, name, value);
                }

            }
        }

使用demo

            //代理,没有就直接传null
            WebProxy proxy = WebCrawl.WebRequestHelper.CreatePorxy("xx.com", "user", "password");

            //根据登录页得到cookie
            CookieContainer cookie = WebCrawl.WebRequestHelper.GetCookie("http://xxxx.login.com", proxy);

            //获取页面
            string html = WebCrawl.WebRequestHelper.Crawl("http://xxx.index.com", proxy, cookie);

            //根据登录页得到cookie字符串
            string cookiestr = WebCrawl.WebRequestHelper.GetCookieString("http://xxxx.login.com", proxy);

            //为webbrowser设置cookie
            WebCrawl.WebRequestHelper.SetCookie(cookiestr, "https://xx.com");

            //获取需要登录切用js生成的页面，当然普通页面也可以
            string htmlWithJs = WebCrawl.WebRequestHelper.CrawlDynamic("http://xxx.index.com");