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

, 19 Oct 2004
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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] PinmemberMember 1027044710-Oct-13 11:22 
QuestionThanks for nice code but Length = 'requestStream.Length' threw an exception of type 'System.NotSupportedException' Pinmembermilindmorey9-Jul-13 4:16 
Questionthanx PinmemberMember 980996929-Apr-13 8:26 
hiii...thanx a lot.its realy good.
but i tried with some is not working . any solution please reply soon
my gmail is ""
Questionhelp, In VB.NET ?? Pinmembermikrophun2-Jul-12 0:15 
AnswerRe: help, In VB.NET ?? Pinmemberclarkwgriswald26-Sep-13 6:43 
Questionany version in ASPX of PHP file ? Pinmemberkiquenet AE12-Dec-11 10:51 
QuestionNot ok for videos file upload PinmemberKKKT25-Jul-11 0:42 
GeneralHCG Ultra Pinmemberrmronimolic15-Jun-10 21:50 
QuestionDoes not work for me, where is my problem? PinmemberSiedlerchr13-Nov-09 3:33 
Generalcancel uploading Pinmemberdjdane13-May-09 8:16 
GeneralRe: cancel uploading Pinmemberkillix14-May-10 1:00 
GeneralThanks Pinmembershahid.here29-Apr-09 5:30 
GeneralNice but Pinmembersabrown10024-Dec-08 5:42 
QuestionSending POST request to aspx pages [modified] Pinmembercinni4-Dec-08 1:38 
GeneralUpload string + file + string PinmemberTravelster661119-Oct-08 2:25 
Generalform data and file upload Pinmembersyed wasif ali27-Jul-08 22:21 
Generalmore files not only one file to upload Pinmemberkappos12-Jun-08 3:23 
GeneralGracias excelente solucion PinmemberMember 310478910-Jun-08 5:29 
GeneralAs another commenter pointed out it's better to close the stream after you're done Pinmemberdolzenko1-Jun-08 9:01 
GeneralAny one know how to decode this type of post Pinmembersmesser3-Jan-08 12:19 
QuestiongetResponse like a web browser? PinmemberEnderwiggin14-Dec-07 11:44 
QuestionWhy it freezes sometimes at requestStream.Write(buffer, 0, bytesRead);? Pinmemberstaryon14-Nov-07 8:31 
GeneralThanks Pinmembercreatorulcom5-Oct-07 13:11 
QuestionWebException Pinmembertobi_z7-Sep-07 13:49 
QuestionHow to send a file a attachment PinmemberPhBV3-Sep-07 3:50 
GeneralParse error in PHP page PinmemberEdYellowMan22-May-07 5:20 
GeneralGreat Job! Pinmemberkkkwkk17-May-07 5:11 
GeneralGet error in Tomcat Pinmemberfranciscomesa28-Apr-07 5:00 
GeneralRe: Get error in Tomcat Pinmembercraighack24-Jun-09 18:36 
GeneralRe: Get error in Tomcat Pinmemberthikon_dew3-Jan-11 23:46 
Generalerrors PinmemberAaron Sulwer9-Aug-06 7:39 
GeneralIO.Exception, Cannot close stream until all bytes are written 21:15 
GeneralPlease Close() your files when done with them!!! PinmemberFurroy19-Jul-06 5:45 
GeneralDid not work for me PinmemberMRKKO17-May-06 7:26 
GeneralRe: Did not work for me PinmemberMystic_20-May-06 4:59 
GeneralRe: Did not work for me PinmemberAaron Sulwer2-Aug-06 11:29 
Generalpost data to PinmemberMystic_27-Apr-06 22:06 
General2nd part PinmemberMystic_27-Apr-06 22:08 
QuestionGetting error as :(406) Not acceptable. PinmemberRahul.P7-Apr-06 0:42 
GeneralWebClient with cookies now possible. Pinmemberkatokay25-Mar-06 6:08 
GeneralRe: WebClient with cookies now possible. Pinmemberu7pro2-Mar-07 5:33 
GeneralRe: WebClient with cookies now possible. Pinmemberkatokay2-Mar-07 6:28 
QuestionRe: WebClient with cookies now possible. PinmemberNickHD22-Apr-07 3:28 
QuestionRe: WebClient with cookies now possible. PinmemberNooklez19-Jun-07 0:37 
AnswerRe: WebClient with cookies now possible. (Wrong) PinmemberAbsolute Solutions11-Jul-07 21:46 
GeneralPOST data Pinmembermorecraf1-Mar-06 5:21 
GeneralRe: POST data Pinmembersatyajeeth20-Feb-07 2:01 
GeneralClosing Boundary Error PinmemberNick Lucas16-Dec-05 6:02 
GeneralRe: Closing Boundary Error PinmemberKartik Ganesan29-Nov-06 12:18 
GeneralProxy problems PinmemberKriG23-Nov-05 3:02 

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