im trying to automate a file upload from my C# program. This is the method to upload a file.
public static string UploadFileEx(string uploadfile, string url,
string fileFormName, string contenttype, NameValueCollection querystring,
CookieContainer cookies)
{
if ((fileFormName == null) ||
(fileFormName.Length == 0))
{
fileFormName = "file";
}
if ((contenttype == null) ||
(contenttype.Length == 0))
{
contenttype = "application/octet-stream";
}
string postdata;
postdata = "";
if (querystring != null)
{
foreach (string key in querystring.Keys)
{
postdata += key + "=" + querystring.Get(key) + "&";
}
}
Uri uri = new Uri(url + postdata);
string boundary = "----------" + DateTime.Now.Ticks.ToString("x");
HttpWebRequest webrequest = (HttpWebRequest)WebRequest.Create(uri);
var sp = webrequest.ServicePoint;
var prop = sp.GetType().GetProperty("HttpBehaviour", BindingFlags.Instance | BindingFlags.NonPublic);
prop.SetValue(sp, (byte)0, null);
webrequest.CookieContainer = cookies;
webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
webrequest.Method = "POST";
webrequest.KeepAlive = true;
webrequest.Referer = "http://www.iwi.hs-karlsruhe.de/scs/simulate/upload.jsp";
webrequest.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
webrequest.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/13.0.782.220 Safari/535.1";
webrequest.Headers.Add("Accept-Language:de-de,de;q=0.8,en-us;q=0.5,en;q=0.3");
webrequest.Headers.Add("Accept-Encoding:gzip, deflate");
webrequest.ProtocolVersion = HttpVersion.Version11;
// Build up the post message header
StringBuilder sb = new StringBuilder();
sb.Append("--");
sb.Append(boundary);
sb.Append("\r\n");
sb.Append("Content-Disposition: form-data; name=\"");
sb.Append(fileFormName);
sb.Append("\"; filename=\"");
sb.Append(Path.GetFileName(uploadfile));
sb.Append("\"");
sb.Append("\r\n");
sb.Append("Content-Type: ");
sb.Append(contenttype);
sb.Append("\r\n");
sb.Append("\r\n");
string postHeader = sb.ToString();
byte[] postHeaderBytes = Encoding.UTF8.GetBytes(postHeader);
// Build the trailing boundary string as a byte array
// ensuring the boundary appears on a line by itself
byte[] boundaryBytes =
Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
FileStream fileStream = new FileStream(uploadfile,
FileMode.Open, FileAccess.Read);
long length = postHeaderBytes.Length + fileStream.Length +
boundaryBytes.Length;
webrequest.ContentLength = length;
Stream requestStream = webrequest.GetRequestStream();
// Write out our post header
requestStream.Write(postHeaderBytes, 0, postHeaderBytes.Length);
// Write out the file contents
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);
// Write out the trailing boundary
requestStream.Write(boundaryBytes, 0, boundaryBytes.Length);
try
{
WebResponse responce = webrequest.GetResponse();
Stream s = responce.GetResponseStream();
StreamReader sr = new StreamReader(s);
return sr.ReadToEnd();
}
catch (Exception ex)
{
return ex.Message;
}
}
When i call it like this on a sample image upload page, everything works fine:
string outdata = UploadFileEx(uploadfile,
"http://www.minpic.de/upload_file.php", "uploadfile0", "image/jpg",
null, null);
But when i try to upload it to the page of my high school it's not working. The upload page is secured by a login form. So i call the upload page to get the initail Cookie, the i post the login credentials and get the right result. So i can see the following upload form:
<form action="../simulate" method=post enctype="multipart/form-data"><br />Choose your inputdata file (xml).<br /><input type=file size=50 maxlength=100000 name="Datei" accept="text/xml"><br><br><input type=submit value="Send"></form>
When i then post the image (i know the expected type is xml but the page answers a error what i want in this case ...) my upload function return a error code 500. Here is what wireshark says for the browsers post:
POST /scs/simulate HTTP/1.1 Host: some host Connection: keep-alive Content-Length: 3874 Cache-Control: max-age=0 Origin: same host User-Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.4 (KHTML, like Gecko) Chrome/22.0.1229.79 Safari/537.4 Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryP3Ti6rxYcN1ov7JD Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8 Referer: some url Accept-Encoding: gzip,deflate,sdch Accept-Language: de-DE,de;q=0.8,en-US;q=0.6,en;q=0.4 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 Cookie: SCS_COOKIE=Default=DE$$MarkePlaceLang=DE; JSESSIONID=B459541362241F66D9312AF157262D25
and here the post from c#:
POST same as above Content-Type: multipart/form-data; boundary=----------8cf828671b8365c Referer: some url Accept: text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.1 (KHTML, like Gecko) Chrome/13.0.782.220 Safari/535.1 Accept-Language: de-de,de;q=0.8,en-us;q=0.5,en;q=0.3 Accept-Encoding: gzip, deflate Host: same host as above Cookie: JSESSIONID=FFE0B7530FFE6A3C8F15FD8A900865B0 Content-Length: 3847 Expect: 100-continue Connection: Keep-Alive
The only difference i can see is the Expect: 100-continue ... Is there a problem with the packet size or something ?
Thx in advance.
you have to upload using multipart. This is shown in your browser post:
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryP3Ti6rxYcN1ov7JD
here is an example: Upload files with HTTPWebrequest (multipart/form-data)
it makes sense because usually image size may be larger than the limit of usual post (2KB or 4KB, I forgot).
来源：https://stackoverflow.com/questions/13101989/c-sharp-httpwebrequest-form-upload