REST calls in XML – VB.NET: How to pass key “file” working in CURL

I have been struggling with this issue for almost a month, I found everything I can find online without any solution. This is my problem: I am implementing a client for a RESTful API service, which must send an XML file in vb.net via a POST call. I was able to Get some data in xml format, but when sending this Xml file, I always get “400 Bad Request Error”.

I have found that it must be a key that must be passed to the server (Obviously only accept POST file uploads, I can’t send it as a string).

Basically this call is used with cURL, but I am trying to implement my own in vb.net Call, pass the correct value.

Working curl call: (Transfer XML successfully)

c:>curl -u username:password -F "file [email protected]" -X POST http://hostname.com/URI?parameters

Vb.net code not working: (this gave me 400 Bad Request)

Dim ss As String = ""'server says...
Dim S As String = txb_username.Text & ":" & txb_password.Text
Dim EncodedString As String = System.Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(S))
Dim req As HttpWebRequest = Nothing
Dim res As HttpWebResponse = Nothing

Try
 Dim xmlDoc As System.Xml.XmlDocument = New System.Xml.XmlDocument
 xmlDoc.XmlResolver = Nothing

 xmlDoc.Load("c:\path\file4.xml")< br />
 Dim sXML As String = "file" & xmlDoc.InnerXml'<- This is wh ere I try to put the "KEY"

 Dim url As String = "http:/host.com+URI"

 req = CType(WebRequest.Create(url) , Net.HttpWebRequest)'or Directcast ... 
 req.Method = "POST"
 req.Headers.Add("Authorization: Basic "& EncodedString)
 req.ContentType = "multipart /form-data"
 req.ContentLength = sXML.Length 
 req.Accept = "*/*"

 System.Windows.Forms.Application.DoEvents()

 Dim sw As System.IO.StreamWriter = New System.IO.StreamWriter(req.GetRequestStream)
 StatusUpdate(sXML)
 sw.Write(sXML)
 sw. Close()
 ss = "server says: "
 res = CType(req.GetResponse, HttpWebResponse)
 StatusUpdate(req.ToString)
 Catch ex As Exception
 StatusUpdate(ss & ex.Message)
Finally

End Try

Is it because I want to send it as a string? (But how can I send it as a file?)
For this, I did another process of sending data bytes, but this one also gave me “400” because (I assume) I didn’t put the “file “Key.

Dim requestStream As Stream = Nothing
 Dim fileStream As FileStream = Nothing
 Dim uploadResponse As Net.HttpWebResponse = Nothing
< br /> Try

 Dim uploadRequest As Net.HttpWebRequest = CType(Net.HttpWebRequest.Create(URI.Text & Uri_part2.text), Net.HttpWebRequest)

 uploadRequest. Method = Net.WebRequestMethods.Http.Post
 uploadRequest.ContentType = "text/xml; charset=utf-8"
 uploadRequest.Credentials = New NetworkCredential("user", "pass")
 uploadRequest.KeepAlive = True
 uploadRequest.UserAgent = "User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10" 
 uploadRequest.Accept = ("text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8")
 uploadRequest.Headers.Add("Accept- Language: en-us,en;q=0.5")
 uplo adRequest.Headers.Add("Accept-Encoding: gzip,deflate")
 uploadRequest.Headers.Add("Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7 ")
 uploadRequest.Headers.Add("Content-Disposition: form-data; name=""file"";")
 uploadRequest.ContentType = "application/xml; charset=utf-8" 

 requestStream = uploadRequest.GetRequestStream()
 fileStream = File.Open("C:\example.xml", FileMode.Open)

 Dim a As Integer 

 Dim buffer(1024) As Byte
 Dim bytesRead As Integer
 While True
 a = a + 1
 bytesRead = fileStream.Read(buffer, 0, buffer.Length)
 StatusUpdate(buffer(a))

 If bytesRead = 0 Then
 Exit While
 End If
 requestStream.Write( buffer, 0, bytesRead)

 End While

 requestStream.Close()

 uploadResponse = uploadRequ est.GetResponse()
 Dim responseReader As StreamReader = New StreamReader(uploadRequest.GetResponse.GetResponseStream())
 Dim x As String = responseReader.ReadToEnd()
 responseReader.Close()
 StatusUpdate(x)


 Catch ex As UriFormatException
 StatusUpdate("UriFormatException: "& ex.Message)
 Catch ex As IOException
 StatusUpdate ("IOException: "& ex.Message)
 Catch ex As Net.WebException
 StatusUpdate("Net.WebException:" & ex.Message)

 Finally
 
 If uploadResponse IsNot Nothing Then
 uploadResponse.Close()
 End If

 If fileStream IsNot Nothing Then
 fileStream.Close()
 End If

 If requestStream IsNot Nothing Then
 requestStream.Close()
 End If

 End Try

In any case, I also tried 2 other clients (POSTMAN and REST console, 2 Google Chrome Extension), I can use it only by adding the value “file” to the “key” field. I have to insert the specific 4 characters “file” to make it work. So, the question is: how to call it in Vb.net To add the same value? How to translate the code called by cURL in the working Vb.net code? Thank you very much for your time and help!

Find the image of what I want to add here,

Attachment: I can’t use PUT, I must use POST (server limit)

I also added To get the HTML code suitable for my purpose, use the server on my computer (see “File” button again)

< br />











 
File 
 
 

In addition, I also pasted a script in PERL, the script It can also be used with the server on my computer.

#!perl

use strict;
use LWP; # Loads all important LWP classes

my $client_id = 1234;
my $filename = "new_file.xml";

### Prepare to make a request

my $browser = LWP::UserAgent->new;

my $url = "http://uri.com?&xx=$client_id" ;

my @post_pairs = (
 #'client_id_in' => $client_id,
'file' => [$filename],
);

my @ns_he aders = (
'User-Agent' =>'Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10',
'Accept' =>'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
'Accept-Language' =>'en-us, en;q=0.5',
'Accept-Encoding' =>'gzip,deflate',
'Accept-Charset' =>'ISO-8859-1,utf-8;q=0.7, *;q=0.7',
'Authorization' =>'Basic base64EncodedCredentialsHere',
'Content_Type' =>'form-data',
);

 ### Make a request
my $response = $browser->post($url, \@post_pairs, @ns_headers);
die "Can't get $url - ", $response- >status_line
 unless $response->is_success;

### Display the response
print STDOUT $response->content;

I think your problem is that you really don’t know what the request should look like, please use fiddler to view the request sent by cURL and try to achieve the same request using vb.net. In my opinion , Your secons code snippet (using a buffer, not an xml serializer) should work…but only on the server side can understand this structure.