Uploading File as FormData in vb.net? - vb.net

Question

I'm having trouble uploading some form data to an API endpoint in vb.net.
Example From Vendor:
curl -X POST -H 'Authorization: Token token=sfg999666t673t7t82'
-H 'Content-Type: multipart/form-data' -H 'content-type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW'
-F file=#/Users/user1/Downloads/download.jpeg -F file_name=nameForFile
-F is_shared=true -F targetable_id=1 -F targetable_type=Lead -X POST "https://domain.freshsales.io/api/documents"
VB.NET CODE
Shameless pulled from (Upload files with HTTPWebrequest (multipart/form-data))
Private Sub HttpUploadFile(ByVal filePath As String, ByVal fileParameterName As String, ByVal contentType As String, ByVal otherParameters As Specialized.NameValueCollection)
Dim boundary As String = "---------------------------" & DateTime.Now.Ticks.ToString("x")
Dim newLine As String = System.Environment.NewLine
Dim boundaryBytes As Byte() = Text.Encoding.ASCII.GetBytes(newLine & "--" & boundary & newLine)
Dim request As Net.HttpWebRequest = Net.WebRequest.Create("https://domain.freshsales.io/api/documents")
request.ContentType = "multipart/form-data; boundary=" & boundary
request.Method = "POST"
request.KeepAlive = True
Using requestStream As IO.Stream = request.GetRequestStream()
Dim formDataTemplate As String = "Content-Disposition: form-data; name=""{0}""{1}{1}{2}"
For Each key As String In otherParameters.Keys
requestStream.Write(boundaryBytes, 0, boundaryBytes.Length)
Dim formItem As String = String.Format(formDataTemplate, key, newLine, otherParameters(key))
Dim formItemBytes As Byte() = Text.Encoding.UTF8.GetBytes(formItem)
requestStream.Write(formItemBytes, 0, formItemBytes.Length)
Next key
requestStream.Write(boundaryBytes, 0, boundaryBytes.Length)
Dim headerTemplate As String = "Content-Disposition: form-data; name=""{0}""; filename=""{1}""{2}Content-Type: {3}{2}{2}"
Dim header As String = String.Format(headerTemplate, fileParameterName, filePath, newLine, contentType)
Dim headerBytes As Byte() = Text.Encoding.UTF8.GetBytes(header)
requestStream.Write(headerBytes, 0, headerBytes.Length)
Using fileStream As New IO.FileStream(filePath, IO.FileMode.Open, IO.FileAccess.Read)
Dim buffer(4096) As Byte
Dim bytesRead As Int32 = fileStream.Read(buffer, 0, buffer.Length)
Do While (bytesRead > 0)
requestStream.Write(buffer, 0, bytesRead)
bytesRead = fileStream.Read(buffer, 0, buffer.Length)
Loop
End Using
Dim trailer As Byte() = Text.Encoding.ASCII.GetBytes(newLine & "--" + boundary + "--" & newLine)
requestStream.Write(trailer, 0, trailer.Length)
End Using
Dim response As Net.WebResponse = Nothing
Try
response = request.GetResponse()
Using responseStream As IO.Stream = response.GetResponseStream()
Using responseReader As New IO.StreamReader(responseStream)
Dim responseText = responseReader.ReadToEnd()
Diagnostics.Debug.Write(responseText)
End Using
End Using
Catch exception As Net.WebException
response = exception.Response
If (response IsNot Nothing) Then
Using reader As New IO.StreamReader(response.GetResponseStream())
Dim responseText = reader.ReadToEnd()
Diagnostics.Debug.Write(responseText)
End Using
response.Close()
End If
Finally
request = Nothing
End Try
End Sub
Calling The Function
Here is my call:
Dim headers As NameValueCollection = New NameValueCollection()
headers.Add("Token", "token=youguessedit;")
Dim nvc As NameValueCollection = New NameValueCollection()
nvc.Add("is_shared", true)
nvc.Add("targetable_id", 1)
nvc.Add("targetable_type", "Lead")
HttpUploadFile("c:\test\file.pdf", "file", "application/pdf", nvc, headers);
I think part of my issue is in the way the headers are attached here:
Dim headerTemplate As String = "Content-Disposition: form-data; name=""{0}""; filename=""{1}""{2}Content-Type: {3}{2}{2}"
In that the API endpoint is expecting file= and file_name= how can I correct the headers?
Can anyone point out where else I have gone wrong? Is there an easier way of doing this?

Answer 1

Here's a simple Console app example using HttpClient with a MultipartFormDataContent which takes care of all the headers and streaming the file, this example also works as-is thanks to Postman-Echo, if there's a requirement for additional headers (only Token is shown here) be sure to add them to the HttpClient.DefaultRequestHeaders
Dim response As New HttpResponseMessage
Dim path As String = "C:\\Temp\\upload.pdf"
Dim uri As New Uri("https://postman-echo.com/post")
Using form As New MultipartFormDataContent,
fs As New FileStream(path, FileMode.Open),
content As New StreamContent(fs),
httpClient As New HttpClient
form.Add(content)
httpClient.DefaultRequestHeaders.Add("Token", "Super Secret")
response = httpClient.PostAsync(uri, form).GetAwaiter.GetResult()
Console.WriteLine("Is Successfull: " & response.IsSuccessStatusCode)
End Using
EDIT: Cleaned up nested Using statements