Send a file via HTTP POST with C

Question

I ve been searching and reading around to that and couldn t fine anything really useful   I m writing an small C  win app that allows user to send files to a web server  not by FTP  but by HTTP using POST  Think of it like a web form but running on a windows application   I have my HttpWebRequest object created using something like this   HttpWebRequest req   WebRequest Create uri  as HttpWebRequest    and also set the Method  ContentType and ContentLength properties  But thats the far I can go   This is my piece of code   HttpWebRequest req   WebRequest Create uri  as HttpWebRequest  req KeepAlive   false  req Method    POST   req Credentials   new NetworkCredential user UserName  user UserPassword   req PreAuthenticate   true  req ContentType   file ContentType  req ContentLength   file Length  HttpWebResponse response   null   try       response   req GetResponse   as HttpWebResponse    catch  Exception e         So my question is basically how can I send a fie  text file  image  audio  etc  with C  via HTTP POST   Thanks

User · Accepted Answer

Using  NET 4 5  or  NET 4 0 by adding the Microsoft Net Http package from NuGet  there is an easier way to simulate form requests  Here is an example   private async Task lt System IO Stream gt  Upload string actionUrl  string paramString  Stream paramFileStream  byte    paramFileBytes        HttpContent stringContent   new StringContent paramString       HttpContent fileStreamContent   new StreamContent paramFileStream       HttpContent bytesContent   new ByteArrayContent paramFileBytes       using  var client   new HttpClient        using  var formData   new MultipartFormDataContent                  formData Add stringContent   param1    param1            formData Add fileStreamContent   file1    file1            formData Add bytesContent   file2    file2            var response   await client PostAsync actionUrl  formData           if   response IsSuccessStatusCode                        return null                    return await response Content ReadAsStreamAsync

User · Answer

Using  NET 4 5 trying to perform form POST file upload  Tried most of the methods above but to no avail  Found the solution here https   www c-sharpcorner com article upload-any-file-using-http-post-multipart-form-data  But I am not not keen as I do not understand why we still need to deal with such low level programming in these common usages  should be handled nicely by framework

User · Answer

For me client UploadFile still wrapped the content in a multipart request so I had to do it like this   using  WebClient client   new WebClient          client Headers Add  Content-Type    application octet-stream        using  Stream fileStream   File OpenRead filePath       using  Stream requestStream   client OpenWrite new Uri fileUploadUrl    POST                  fileStream CopyTo requestStream

User · Answer

To post files as from byte arrays   private static string UploadFilesToRemoteUrl string url  IList lt byte   gt  files  NameValueCollection nvc             string boundary    ----------------------------    DateTime Now Ticks ToString  x             var request    HttpWebRequest  WebRequest Create url           request ContentType    multipart form-data  boundary     boundary          request Method    POST           request KeepAlive   true          var postQueue   new ByteArrayCustomQueue             var formdataTemplate     r n--    boundary     r nContent-Disposition  form-data  name    0     r n r n 1             foreach  string key in nvc Keys                var formitem   string Format formdataTemplate  key  nvc key                var formitembytes   Encoding UTF8 GetBytes formitem               postQueue Write formitembytes                      var headerTemplate     r n--    boundary     r n                 Content-Disposition  form-data  name    0     filename    1    r n                  Content-Type  application zip r n r n            var i   0          foreach  var file in files                var header   string Format headerTemplate   file    i   file    i     zip                var headerbytes   Encoding UTF8 GetBytes header               postQueue Write headerbytes               postQueue Write file               i                       postQueue Write Encoding UTF8 GetBytes   r n--    boundary    --              request ContentLength   postQueue Length           using  var requestStream   request GetRequestStream                  postQueue CopyToStream requestStream               requestStream Close                       var webResponse2   request GetResponse             using  var stream2   webResponse2 GetResponseStream            using  var reader2   new StreamReader stream2                  var res    reader2 ReadToEnd                webResponse2 Close                return res                   public class ByteArrayCustomQueue        private LinkedList lt byte   gt  arrays   new LinkedList lt byte   gt               lt summary gt          Writes the specified data           lt  summary gt           lt param name  data  gt The data  lt  param gt      public void Write byte   data            arrays AddLast data                   lt summary gt          Gets the length           lt  summary gt           lt value gt          The length           lt  value gt      public int Length   get   return arrays Sum x   gt  x Length                 lt summary gt          Copies to stream           lt  summary gt           lt param name  requestStream  gt The request stream  lt  param gt           lt exception cref  System NotImplementedException  gt  lt  exception gt      public void CopyToStream Stream requestStream            foreach  var array in arrays                requestStream Write array  0  array Length

User · Answer

public string SendFile string filePath                                WebResponse response   null                  try                                       string sWebAddress    Https   www address com                        string boundary    ---------------------------    DateTime Now Ticks ToString  x                        byte   boundarybytes   System Text Encoding ASCII GetBytes   r n--    boundary     r n                        HttpWebRequest wr    HttpWebRequest WebRequest Create sWebAddress                       wr ContentType    multipart form-data  boundary     boundary                      wr Method    POST                       wr KeepAlive   true                      wr Credentials   System Net CredentialCache DefaultCredentials                      Stream stream   wr GetRequestStream                        string formdataTemplate    Content-Disposition  form-data  name    0    r n r n 1                         stream Write boundarybytes  0  boundarybytes Length                       byte   formitembytes   System Text Encoding UTF8 GetBytes filePath                       stream Write formitembytes  0  formitembytes Length                       stream Write boundarybytes  0  boundarybytes Length                       string headerTemplate    Content-Disposition  form-data  name    0     filename    1    r nContent-Type   2  r n r n                       string header   string Format headerTemplate   file   Path GetFileName filePath   Path GetExtension filePath                        byte   headerbytes   System Text Encoding UTF8 GetBytes header                       stream Write headerbytes  0  headerbytes Length                        FileStream fileStream   new FileStream filePath  FileMode Open  FileAccess Read                       byte   buffer   new byte 4096                       int bytesRead   0                      while   bytesRead   fileStream Read buffer  0  buffer Length      0                          stream Write buffer  0  bytesRead                       fileStream Close                         byte   trailer   System Text Encoding ASCII GetBytes   r n--    boundary    -- r n                        stream Write trailer  0  trailer Length                       stream Close                         response   wr GetResponse                        Stream responseStream   response GetResponseStream                        StreamReader streamReader   new StreamReader responseStream                       string responseData   streamReader ReadToEnd                        return responseData                                    catch  Exception ex                                        return ex Message                                    finally                                       if  response    null                          response Close

User · Answer

I had got the same problem and this following code answered perfectly at this problem      Identificate separator string boundary    ---------------------------    DateTime Now Ticks ToString  x      Encoding byte   boundarybytes   System Text Encoding ASCII GetBytes   r n--    boundary     r n       Creation and specification of the request HttpWebRequest wr    HttpWebRequest WebRequest Create url     sVal is id for the webService wr ContentType    multipart form-data  boundary     boundary  wr Method    POST   wr KeepAlive   true  wr Credentials   System Net CredentialCache DefaultCredentials   string sAuthorization    login password    AUTHENTIFICATION BEGIN byte   toEncodeAsBytes   System Text ASCIIEncoding ASCII GetBytes sAuthorization   string returnValue   System Convert ToBase64String toEncodeAsBytes   wr Headers Add  Authorization  Basic     returnValue     AUTHENTIFICATION END Stream rs   wr GetRequestStream      string formdataTemplate    Content-Disposition  form-data  name    0    r n r n 1      For the POST s format    Writting of the file rs Write boundarybytes  0  boundarybytes Length   byte   formitembytes   System Text Encoding UTF8 GetBytes Server MapPath  questions pdf     rs Write formitembytes  0  formitembytes Length    rs Write boundarybytes  0  boundarybytes Length    string headerTemplate    Content-Disposition  form-data  name    0     filename    1    r nContent-Type   2  r n r n   string header   string Format headerTemplate   file    questions pdf   contentType   byte   headerbytes   System Text Encoding UTF8 GetBytes header   rs Write headerbytes  0  headerbytes Length    FileStream fileStream   new FileStream Server MapPath  questions pdf    FileMode Open  FileAccess Read   byte   buffer   new byte 4096   int bytesRead   0  while   bytesRead   fileStream Read buffer  0  buffer Length      0        rs Write buffer  0  bytesRead     fileStream Close     byte   trailer   System Text Encoding ASCII GetBytes   r n--    boundary    -- r n    rs Write trailer  0  trailer Length   rs Close    rs   null   WebResponse wresp   null  try         Get the response     wresp   wr GetResponse        Stream stream2   wresp GetResponseStream        StreamReader reader2   new StreamReader stream2       string responseData   reader2 ReadToEnd      catch  Exception ex        string s   ex Message    finally       if  wresp    null                wresp Close            wresp   null            wr   null

User · Answer

To send the raw file only   using WebClient client   new WebClient          client UploadFile address  filePath       If you want to emulate a browser form with an  lt input type  file   gt   then that is harder  See this answer for a multipart form-data answer

User · Answer

You need to write your file to the request stream   using  var reqStream   req GetRequestStream               reqStream Write           write the bytes of the file

[c#] Send a file via HTTP POST with C#

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