c# 爬虫（三） 文件上传
2021-05-27 22:03
阅读：545
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 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;
}
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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
Dictionarydic.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);
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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。
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