HttpWebRequest类与HttpRequest类的区别。

　　HttpRequest类的对象用于服务器端，获取客户端传来的请求的信息，包括HTTP报文传送过来的所有信息。而HttpWebRequest用于客户端，拼接请求的HTTP报文并发送等。

　　HttpWebRequest这个类非常强大，强大的地方在于它封装了几乎HTTP请求报文里需要用到的东西，以致于能够能够发送任意的HTTP请求并获得服务器响应(Response)信息。采集信息常用到这个类。在学习这个类之前，首先有必要了解下HTTP方面的知识。

一、简单示例

　　我们先来一个最简单的，就是紧紧输入一个网址就获取响应。代码如下：

class Program    {        static void Main(string[] args)        {            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://www.baidu.com");    //创建一个请求示例            HttpWebResponse response  = (HttpWebResponse)request.GetResponse();　　//获取响应，即发送请求            Stream responseStream = response.GetResponseStream();            StreamReader streamReader = new StreamReader(responseStream, Encoding.UTF8);            string html = streamReader.ReadToEnd();            Console.WriteLine(html);            Console.ReadKey();        }    }

　　OK，就是这么简单了，真的这么简单吗？发送一个HTTP请求真的这么简单。但是要做出很多功能就不简单了。你需要详细了解下HTTP方面的知识，比如HTTP请求报文之类的。

二、模拟登录

　　下面来个复杂点的，这次是获取登录之后的页面。登录之后的请求用什么实现呢？呵呵，用到是cookie。在拼接HTTP请求的时候，连着cookie也发送过去。

namespace ConsoleApplication1{    class Program    {        static void Main(string[] args)        {            HttpHeader header = new HttpHeader();            header.accept = "image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/x-silverlight, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, application/x-silverlight-2-b1, */*";            header.contentType = "application/x-www-form-urlencoded";            header.method = "POST";            header.userAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022)";            header.maxTry = 300;            //在这里自己拼接一下Cookie，不用复制过来的那个GetCookie方法了，原来的那个写法还是比较严谨的            CookieContainer cc = new CookieContainer();            Cookie cUserName = new Cookie("cSpaceUserEmail", "742783833%40qq.com");            cUserName.Domain = ".7soyo.com";            Cookie cUserPassword = new Cookie("cSpaceUserPassWord", "4f270b36a4d3e5ee70b65b1778e8f793");            cUserPassword.Domain = ".7soyo.com";            cc.Add(cUserName);            cc.Add(cUserPassword);            string html = HTMLHelper.GetHtml("http://user.7soyo.com/CollectUser/List", cc, header);            FileStream fs = new FileStream(@"D:\123.txt",FileMode.CreateNew,FileAccess.ReadWrite);            fs.Write(Encoding.UTF8.GetBytes(html),0,html.Length);            fs.Flush();            fs.Dispose();            Console.WriteLine(html);            Console.ReadKey();        }    }    public class HTMLHelper    {        /// 
        /// 获取CooKie        /// 
        ///         ///         ///         /// 
             public static CookieContainer GetCooKie(string loginUrl, string postdata, HttpHeader header)        {            HttpWebRequest request = null;            HttpWebResponse response = null;            try            {                CookieContainer cc = new CookieContainer();                request = (HttpWebRequest)WebRequest.Create(loginUrl);                request.Method = header.method;                request.ContentType = header.contentType;                byte[] postdatabyte = Encoding.UTF8.GetBytes(postdata);     //提交的请求主体的内容                request.ContentLength = postdatabyte.Length;    //提交的请求主体的长度                request.AllowAutoRedirect = false;                request.CookieContainer = cc;                request.KeepAlive = true;                //提交请求                Stream stream;                stream = request.GetRequestStream();                stream.Write(postdatabyte, 0, postdatabyte.Length);     //带上请求主体                stream.Close();                //接收响应                response = (HttpWebResponse)request.GetResponse();      //正式发起请求                response.Cookies = request.CookieContainer.GetCookies(request.RequestUri);                CookieCollection cook = response.Cookies;                //Cookie字符串格式                string strcrook = request.CookieContainer.GetCookieHeader(request.RequestUri);                return cc;            }            catch (Exception ex)            {                throw ex;            }        }        /// 
        /// 获取html        /// 
        ///         ///         ///         /// 
             public static string GetHtml(string getUrl, CookieContainer cookieContainer, HttpHeader header)        {            Thread.Sleep(1000);            HttpWebRequest httpWebRequest = null;            HttpWebResponse httpWebResponse = null;            try            {                httpWebRequest = (HttpWebRequest)HttpWebRequest.Create(getUrl);                httpWebRequest.CookieContainer = cookieContainer;                httpWebRequest.ContentType = header.contentType;                httpWebRequest.ServicePoint.ConnectionLimit = header.maxTry;                httpWebRequest.Referer = getUrl;                httpWebRequest.Accept = header.accept;                httpWebRequest.UserAgent = header.userAgent;                httpWebRequest.Method = "GET";                httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();                Stream responseStream = httpWebResponse.GetResponseStream();                StreamReader streamReader = new StreamReader(responseStream, Encoding.UTF8);                string html = streamReader.ReadToEnd();                streamReader.Close();                responseStream.Close();                httpWebRequest.Abort();                httpWebResponse.Close();                return html;            }            catch (Exception e)            {                if (httpWebRequest != null) httpWebRequest.Abort();                if (httpWebResponse != null) httpWebResponse.Close();                return string.Empty;            }        }    }    public class HttpHeader    {        public string contentType { get; set; }        public string accept { get; set; }        public string userAgent { get; set; }        public string method { get; set; }        public int maxTry { get; set; }    }}

　　这样获取到的就是登录之后的页面了。

三、模拟表单提交

　　再来一个例子，运用HttpWebRequest来模拟表单的提交，先新建一个MVC项目，里面只有这些代码：

[HttpPost]        public ActionResult Index(string userName,string userPassword)        {            string str = "你提交过来的用户名是:" + userName + ",密码是: " + userPassword;            Response.Write(str);            return View();        }

　　然后启动该项目，再新建另外一个项目,用于模拟提交表单，然后注意路径填写的是刚才建的那个MVC项目。

static void Main(string[] args)        {            HttpWebRequest request = null;            HttpWebResponse response = null;            CookieContainer cc = new CookieContainer();            request = (HttpWebRequest)WebRequest.Create("http://localhost:2539/");            request.Method = "POST";            request.ContentType = "application/x-www-form-urlencoded";            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; rv:19.0) Gecko/20100101 Firefox/19.0";            string requestForm = "userName=1693372175&userPassword=123456";     //拼接Form表单里的信息            byte[] postdatabyte = Encoding.UTF8.GetBytes(requestForm);            request.ContentLength = postdatabyte.Length;            request.AllowAutoRedirect = false;            request.CookieContainer = cc;            request.KeepAlive = true;            Stream stream;            stream = request.GetRequestStream();            stream.Write(postdatabyte, 0, postdatabyte.Length); //设置请求主体的内容            stream.Close();            //接收响应            response = (HttpWebResponse)request.GetResponse();            Console.WriteLine();            Stream stream1 = response.GetResponseStream();            StreamReader sr = new StreamReader(stream1);            Console.WriteLine(sr.ReadToEnd());                    Console.ReadKey();        }

　　输出结果如下所示：

　　

四、模拟上传

　　血的教训，注意路径不能写错，否则在对流进行操作时，Write，就会报错：

HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://localhost:9170/upload/test");

　　客户端：

class Program    {        /**          * 如果要在客户端向服务器上传文件，我们就必须模拟一个POST multipart/form-data类型的请求          * Content-Type必须是multipart/form-data。          * 以multipart/form-data编码的POST请求格式与application/x-www-form-urlencoded完全不同          * multipart/form-data需要首先在HTTP请求头设置一个分隔符,例如7d4a6d158c9：          * 我们模拟的提交要设定 content-type不同于非含附件的post时候的content-type          * 这里需要： ("Content-Type", "multipart/form-data; boundary=ABCD");          * 然后，将每个字段用“--7d4a6d158c9”分隔，最后一个“--7d4a6d158c9--”表示结束。          * 例如，要上传一个title字段"Today"和一个文件C:\1.txt，HTTP正文如下：          *           * --7d4a6d158c9          * Content-Disposition: form-data; name="title"          * \r\n\r\n          * Today          * --7d4a6d158c9          * Content-Disposition: form-data; name="1.txt"; filename="C:\1.txt"          * Content-Type: text/plain          * 如果是图片Content-Type: application/octet-stream          * \r\n\r\n          * 
     <这里是1.txt文件的内容>
                * --7d4a6d158c9          * \r\n          * 请注意，每一行都必须以\r\n结束value前面必须有2个\r\n，包括最后一行。         */        static void Main(string[] args)        {            string boundary = "----------" + DateTime.Now.Ticks.ToString("x");//元素分割标记             StringBuilder sb = new StringBuilder();            sb.Append("--" + boundary);            sb.Append("\r\n");            sb.Append("Content-Disposition: form-data; name=\"file1\"; filename=\"D:\\upload.xml" + "\"");            sb.Append("\r\n");            sb.Append("Content-Type: application/octet-stream");            sb.Append("\r\n");            sb.Append("\r\n");//value前面必须有2个换行              HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://localhost:9170/upload/test");            request.ContentType = "multipart/form-data; boundary=" + boundary;//其他地方的boundary要比这里多--              request.Method = "POST";            FileStream fileStream = new FileStream(@"D:\123.xml", FileMode.OpenOrCreate, FileAccess.Read);            byte[] postHeaderBytes = Encoding.UTF8.GetBytes(sb.ToString());            byte[] boundaryBytes = Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");            //http请求总长度              request.ContentLength = postHeaderBytes.Length + fileStream.Length + boundaryBytes.Length;            Stream requestStream = request.GetRequestStream();             requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);            byte[] buffer = new Byte[checked((uint)Math.Min(4096, (int)fileStream.Length))];            int bytesRead = 0;            while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)            {                requestStream.Write(buffer, 0, bytesRead);            }            fileStream.Dispose();            requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);            WebResponse webResponse2 = request.GetResponse();            Stream htmlStream = webResponse2.GetResponseStream();            string HTML = GetHtml(htmlStream, "UTF-8");            Console.WriteLine(HTML);            htmlStream.Dispose();        } 　　}
     

　　测试服务器端地址：

public ActionResult Test()        {            HttpRequest request = System.Web.HttpContext.Current.Request;            HttpFileCollection FileCollect = request.Files;            if (FileCollect.Count > 0)          //如果集合的数量大于0            {                foreach (string str in FileCollect)                {                    HttpPostedFile FileSave = FileCollect[str];  //用key获取单个文件对象HttpPostedFile                    string imgName = DateTime.Now.ToString("yyyyMMddhhmmss");                    string AbsolutePath = FileSave.FileName;                    FileSave.SaveAs(AbsolutePath);              //将上传的东西保存                }            }            return Content("键值对数目：" + FileCollect.Count);        }

　　参考：

 　　其实还有很多东西的，比如模拟下载等等。这个留到以后用到再研究了。