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Posted 19 Oct 2004


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UploadFileEx: C#'s WebClient.UploadFile with more functionality

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4.81/5 (33 votes)
19 Oct 20041 min read
UploadFile hides some of the things you might need to get your Windows client simulating forms with file input fields. UploadFileEx gives you more control where you need it!


Okay, so you like the idea behind WebClient's UploadFile function, but you can't get it to do all the things you want? That's were I was at a week ago. This is what I learned in the past week. UploadFile seems good enough on the surface but you can run into some tricky things fast, like if you have some cookies to manage or you want to specify the content type, or change the name of the file input in the form? Well, this function will take care of those problems and should make simulating a web form with input type=file as easy as pi, er.. pie. Under the hood is a HttpWebRequest version of UploadFile that you could use to add additional functionality.

For example...

You would like to simulate this web form from your C# application:

<form action ="http://localhost/test.php" method = POST>
<input type = text name = uname>
<input type = password name =passwd>
<input type = FILE name = uploadfile>
<input type=submit>

You could run UploadFileEx like this:

CookieContainer cookies = new CookieContainer();
//add or use cookies
NameValueCollection querystring = new NameValueCollection();
string uploadfile;// set to file to upload
uploadfile = "c:\\test.jpg";

//everything except upload file and url can be left blank if needed
string outdata = UploadFileEx(uploadfile, 
     "http://localhost/test.php","uploadfile", "image/pjpeg", 

So on to the code...

So, this is UploadFileEx:

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);
    webrequest.CookieContainer = cookies;
    webrequest.ContentType = "multipart/form-data; boundary=" + boundary;
    webrequest.Method = "POST";

    // Build up the post message header
    StringBuilder sb = new StringBuilder();
    sb.Append("Content-Disposition: form-data; name=\"");
    sb.Append("\"; filename=\"");
    sb.Append("Content-Type: ");

    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 + 
    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 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);
    WebResponse responce = webrequest.GetResponse();
    Stream s = responce.GetResponseStream();
    StreamReader sr = new StreamReader(s);

    return sr.ReadToEnd();

This might help too..

You can handle the post in various ways but this is the PHP file I wrote to test:



$uploadDir = '%SOMEPATH';
$uploadFile = $uploadDir . $_FILES['userfile']['name'];
print "<PRE>";
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadFile))
    print "File is valid, and was successfully uploaded. ";
    print "Possible file upload attack!  Here's some debugging info:\n";
print "</PRE>";


I found most of this out by trial and error searching the web. One major source of this information was this article.


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Comments and Discussions

BugUsing this code gave me 400 Bad request (malformed multipart POST) errors [Solved] Pin
Member 1027044710-Oct-13 10:22
MemberMember 1027044710-Oct-13 10:22 
QuestionThanks for nice code but Length = 'requestStream.Length' threw an exception of type 'System.NotSupportedException' Pin
Milind_Morey9-Jul-13 3:16
professionalMilind_Morey9-Jul-13 3:16 
Questionthanx Pin
Member 980996929-Apr-13 7:26
MemberMember 980996929-Apr-13 7:26 
Questionhelp, In VB.NET ?? Pin
mikrophun1-Jul-12 23:15
Membermikrophun1-Jul-12 23:15 
AnswerRe: help, In VB.NET ?? Pin
danglez8326-Sep-13 5:43
Memberdanglez8326-Sep-13 5:43 
Questionany version in ASPX of PHP file ? Pin
kiquenet.com12-Dec-11 9:51
professionalkiquenet.com12-Dec-11 9:51 
QuestionNot ok for videos file upload Pin
KKKT24-Jul-11 23:42
MemberKKKT24-Jul-11 23:42 
GeneralHCG Ultra Pin
rmronimolic15-Jun-10 20:50
Memberrmronimolic15-Jun-10 20:50 
QuestionDoes not work for me, where is my problem? Pin
Siedlerchr13-Nov-09 2:33
MemberSiedlerchr13-Nov-09 2:33 
Generalcancel uploading Pin
djdane13-May-09 7:16
Memberdjdane13-May-09 7:16 
GeneralRe: cancel uploading Pin
killix14-May-10 0:00
Memberkillix14-May-10 0:00 
GeneralThanks Pin
shahid.here29-Apr-09 4:30
Membershahid.here29-Apr-09 4:30 
GeneralNice but Pin
sabrown10024-Dec-08 4:42
Membersabrown10024-Dec-08 4:42 
QuestionSending POST request to aspx pages [modified] Pin
Cinni4-Dec-08 0:38
MemberCinni4-Dec-08 0:38 
GeneralUpload string + file + string Pin
Travelster661119-Oct-08 1:25
MemberTravelster661119-Oct-08 1:25 
Generalform data and file upload Pin
syed wasif ali27-Jul-08 21:21
Membersyed wasif ali27-Jul-08 21:21 
Generalmore files not only one file to upload Pin
kappos12-Jun-08 2:23
Memberkappos12-Jun-08 2:23 
GeneralGracias excelente solucion Pin
Member 310478910-Jun-08 4:29
MemberMember 310478910-Jun-08 4:29 
GeneralAs another commenter pointed out it's better to close the stream after you're done Pin
dolzenko1-Jun-08 8:01
Memberdolzenko1-Jun-08 8:01 
GeneralAny one know how to decode this type of post Pin
Steve Messer3-Jan-08 11:19
MemberSteve Messer3-Jan-08 11:19 
QuestiongetResponse like a web browser? Pin
Enderwiggin14-Dec-07 10:44
MemberEnderwiggin14-Dec-07 10:44 
QuestionWhy it freezes sometimes at requestStream.Write(buffer, 0, bytesRead);? Pin
LEM314-Nov-07 7:31
MemberLEM314-Nov-07 7:31 
GeneralThanks Pin
bogdandanielb5-Oct-07 12:11
Memberbogdandanielb5-Oct-07 12:11 
QuestionWebException Pin
tobi_z7-Sep-07 12:49
Membertobi_z7-Sep-07 12:49 
QuestionHow to send a file a attachment Pin
PhBV3-Sep-07 2:50
MemberPhBV3-Sep-07 2:50 

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