(VB.NET UWP/WinRT) REST Stream Multipart Body from File

Demonstrates how to send a multipart/form-data HTTP request, where one of the parts contains data streamed directly from a file. This is good for cases where the file to be uploaded is very large.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads

Chilkat for the Universal Windows Platform (UWP)

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim rest As New Chilkat.Rest

' Connect to the destination web server.
Dim bTls As Boolean = True
Dim port As Integer = 443
Dim bAutoReconnect As Boolean = True
Dim success As Boolean = Await rest.ConnectAsync("www.somewebserver.com",port,bTls,bAutoReconnect)

' This example will send the following multipart/form-data request.
' The Content-Length is automatically computed and added by Chilkat.

' 	POST /some_path HTTP/1.1
' 	Content-Type: multipart/form-data; boundary=---------------------------735323031399963166993862150
' 	Content-Length: 834
' 
' 	-----------------------------735323031399963166993862150
' 	Content-Disposition: form-data; name="text1"
' 
' 	text 123 abc
' 	-----------------------------735323031399963166993862150
' 	Content-Disposition: form-data; name="text2"
' 
' 	xyz
' 	-----------------------------735323031399963166993862150
' 	Content-Disposition: form-data; name="file1"; filename="a.txt"
' 	Content-Type: text/plain
' 
' 	Content of a.txt.
' 
' 	-----------------------------735323031399963166993862150
' 	Content-Disposition: form-data; name="file2"; filename="a.html"
' 	Content-Type: text/html
' 
' 	<!DOCTYPE html><title>Content of a.html.</title>
' 
' 	-----------------------------735323031399963166993862150
' 	Content-Disposition: form-data; name="file3"; filename="starfish.jpg"
' 	Content-Type: image/jpeg
' 
' 	binary data goes here
' 	-----------------------------735323031399963166993862150--

' Set the Content-Type for the topmost MIME part.
rest.AddHeader("Content-Type","multipart/form-data")

' Specify each part of the request.
rest.PartSelector = "1"
rest.AddHeader("Content-Disposition","form-data; name=""text1""")
rest.SetMultipartBodyString("text 123 abc")

rest.PartSelector = "2"
rest.AddHeader("Content-Disposition","form-data; name=""text2""")
rest.SetMultipartBodyString("xyz")

rest.PartSelector = "3"
rest.AddHeader("Content-Disposition","form-data; name=""file1""; filename=""a.txt""")
rest.AddHeader("Content-Type","text/plain")
rest.SetMultipartBodyString("Content of a.txt.")

rest.PartSelector = "4"
rest.AddHeader("Content-Disposition","form-data; name=""file2""; filename=""a.html""")
rest.AddHeader("Content-Type","text/html")
Dim sbHtml As New Chilkat.StringBuilder
sbHtml.LoadFile("qa_data/html/a.html","utf-8")
rest.SetMultipartBodySb(sbHtml)

rest.PartSelector = "5"
rest.AddHeader("Content-Disposition","form-data; name=""file3""; filename=""starfish.jpg""")
rest.AddHeader("Content-Type","image/jpeg")

' When the request is sent, stream this part directly from the file.
' This avoids having to load the entire file into memory.
Dim fileStream As New Chilkat.Stream
fileStream.SourceFile = "qa_data/jpg/starfish.jpg"
rest.SetMultipartBodyStream(fileStream)

Dim responseBody As String = Await rest.FullRequestMultipartAsync("POST","/some_path")
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' ...
' ...

' Clear the REST object for any subsequent requests..
rest.ClearAllHeaders()
rest.ClearAllParts()
rest.PartSelector = ""