c# 爬虫（三） 文件上传

在上一篇中，我们说了模拟登录，

下面我们说说附件上传。

据说，最早的http协议是不支持附件上传的，后来有添加了一个RFC 2045 协议，才支持附件上传，关于附件上传，请参见

http://www.cnblogs.com/greenerycn/archive/2010/05/15/csharp_http_post.html

好了，其实用C#模拟上传附件，主要的难点就在于如何构建此协议的格式以及编码。

作为备忘，我这里只放一段成品代码了。

参数：URL,上传控件的id，附件的本地全路径，传输的Key-value数据

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public string HttpWebUpload(string url, string fileControlID, string fileFullPath, Dictionary<string, string> dic)         {             string fileContentType = "application/octet-stream";//"application/octet-stream";//"text/plain";//image/jpeg                        int index = fileFullPath.LastIndexOf('\');             string filename = fileFullPath.Substring(index+1);                           var boundary = DateTime.Now.Ticks.ToString("x");             var beginBoundary = "--" + boundary;             var reqContentType = "multipart/form-data; boundary=" + boundary;               var memStream = new MemoryStream();             var fileStream = new FileStream(fileFullPath, FileMode.Open, FileAccess.Read);             int fsLen = (int)fileStream.Length;             byte[] btfileValue = new byte[fsLen];             int r = fileStream.Read(btfileValue, 0, btfileValue.Length);               StringBuilder fileHeader = new StringBuilder();             fileHeader.AppendLine(beginBoundary);             fileHeader.AppendLine(string.Format("Content-Disposition: form-data; name="{0}"; filename="{1}"", fileControlID, filename));             fileHeader.AppendLine(string.Format("Content-Type: {0}", fileContentType));             fileHeader.AppendLine();             var btfileKey = Encoding.UTF8.GetBytes(fileHeader.ToString());               StringBuilder dicData = new StringBuilder();             dicData.AppendLine();             foreach (var item in dic)             {                   dicData.AppendLine(beginBoundary);                 dicData.AppendLine(string.Format("Content-Disposition:form-data; name="{0}"", item.Key));                 dicData.AppendLine();                 dicData.AppendLine(item.Value);             }               dicData.AppendLine(beginBoundary + "--");             var btDic = Encoding.UTF8.GetBytes(dicData.ToString());               HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);             req.Method = "POST";             req.AllowAutoRedirect = false;             req.ContentType = reqContentType;             if (!string.IsNullOrEmpty(UserAgent))             {                 req.UserAgent = this.UserAgent;             }               if (!string.IsNullOrEmpty(Cookie))             {                 req.CookieContainer = new CookieContainer();                 req.CookieContainer.SetCookies(req.RequestUri, this.Cookie);             }               req.ContentLength = btfileKey.Length + btfileValue.Length + btDic.Length;             Stream postDataStream = req.GetRequestStream();             postDataStream.Write(btfileKey, 0, btfileKey.Length);             postDataStream.Write(btfileValue, 0, btfileValue.Length);             postDataStream.Write(btDic, 0, btDic.Length);             postDataStream.Close();               HttpWebResponse resp = (HttpWebResponse)req.GetResponse();             string html = new StreamReader(resp.GetResponseStream()).ReadToEnd();             return html;         }

　　注意，这里如果需要cookie,则添加对应的cookie。

调用方法

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string controlid = "fupCert"; string filefullPath = "f:\3.pdf"; string url = "http://10.35.3.240/NT_HandbookExtend/FrmCertificate.aspx?type=N&zdtype=J&DELEGATENO=SBWJ16100001&ID=SB20161018000001%2c3206960757&Action=Modify&manualRecordID=SL20161018000001&tm=0.17032586549994377";   var hiddenVal = web.GetDoNetHiddenValuesByUrl(url);//获取__VIEWSTATE，与__EVENTVALIDATION隐藏域值   Dictionary<string, string> dic = new Dictionary<string, string>(); dic.Add("__EVENTARGUMENT", ""); dic.Add("__EVENTTARGET", "btnUpload"); dic.Add("__EVENTVALIDATION", hiddenVal.Eventvalidation); dic.Add("__PREVIOUSPAGE", "EncayjCF95BJXxMazWGgd9UdPYeLp64GjuJlZ-rvnQ5n34-y7KQYllE35nAdVFvk0"); dic.Add("__VIEWSTATE", hiddenVal.Vievstate); dic.Add("__VIEWSTATEENCRYPTED", ""); dic.Add("grdNavigatorPRE_EMS3_CUS_IMG$ctl06", ""); dic.Add("grdNavigatorPRE_EMS3_CUS_IMG$ctl07", "15"); dic.Add("grdNavigatorPRE_EMS3_CUS_IMG$labelRowCount", "8"); dic.Add("hfERP", "http://www.nteport.gov.cn/cerp/platform/erp/documentManagement/documentDocking.jsp"); dic.Add("hidFileType", "333"); dic.Add("hidID", ""); //web.UserAgent = "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0)"; string html = web.HttpWebUpload(url, controlid, filefullPath, dic);

　　

其他注意事项：

1.如果不限制文件类型，请使用 ContentType = "application/octet-stream";这个我也没怎么懂，尴尬。。。

2. 编码很重要，由于传参时，都是以流的形式传参，所以文件编码使用默认的编码方式，和其他构建的RFC 2045 协议格式，使用UTF-8编码。