(VB.NET) Building a multipart/form-data Request for HTTP Upload

Uploading files to a web server typically requires building a multipart/form-data request where the files are contained in the sub-parts of the MIME request.

Note: HTTP uploads require code on the server-side to receive the upload. For example, see Complete C# ASP.NET HTTP Upload Example

This example produces the following HTTP multipart/form-data request:

POST /something HTTP/1.1
Content-Type: multipart/form-data; boundary=------------070002080409050901090203
Host: domain
Content-Length: 546

--------------070002080409050901090203
Content-Disposition: form-data; name="fileA"; filename="fileA.txt"
Content-Type: text/plain

This is the contents of file A
--------------070002080409050901090203
Content-Disposition: form-data; name="fileB"; filename="fileB.txt"
Content-Type: text/plain

This is the contents of file B
--------------070002080409050901090203
Content-Disposition: form-data; name="fileC"; filename="fileC.txt"
Content-Type: text/plain

This is the contents of file C
--------------070002080409050901090203--

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' This example demonstrates building a multipart/form-data request.

Dim req As New Chilkat.HttpRequest

' The ContentType, HttpVerb, and Path properties should
' always be explicitly set.
req.HttpVerb = "POST"
req.Path = "/something"
req.ContentType = "multipart/form-data"

' The contents and name of each file to be uploaded is provided
' by calling any of the following methods:
' AddBytesForUpload
' AddBytesForUpload2
' AddFileForUpload
' AddFileForUpload2
' AddStringForUpload
' AddStringForUpload2

' For this example, we'll provide the contents of the files to be uploaded
' directly as in-memory strings.
req.AddStringForUpload("fileA","fileA.txt","This is the contents of file A","utf-8")
req.AddStringForUpload("fileB","fileB.txt","This is the contents of file B","utf-8")
req.AddStringForUpload("fileC","fileC.txt","This is the contents of file C","utf-8")

' View the request that would be sent if SynchronousRequest was called:
Dim requestMime As String = req.GenerateRequestText()
Debug.WriteLine(requestMime)

' A few important comments about the HTTP request that is generated:
' 
' 1) Chilkat automatically generates a random boundary string.   In 99.999% of cases, this should 
'    be sufficient.
' 2) The Content-Length header is automatically generated based on the actual length of the MIME message
'    that follows the intial (topmost) MIME header.
' 3) The HOST header will automatically get filled in with the actual domain when SynchronousRequest
'    is called