(VB.NET) Download GMail Message Attachment by ID

Demonstrates how to download a GMail email attachment by the attachment ID.

For more information, see https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

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

Dim http As New Chilkat.Http
Dim success As Boolean

http.AuthToken = "ACCESS_TOKEN"
http.Accept = "application/json"

' See the following example:  Get GMail Message (format=full)
' It shows how to download an email by message ID, and it shows how to parse the JSON
' response which includes attachment names, ids, and other information.

' This example will assume we already have the attachment id and filename.

' This is the attachment ID for a file named "helloWorld.pdf".
Dim attachmentId As String = "ANGjdJ-oy3aCuZISJKLAhUdaEksCEklbAPyMaWzFgqOMGbPCRkgwgeu_Kttd99C17OBTHROkDZGekibTKWXGfscB5ww7fw4E65_V1dQ-jHhb2TD1Cdm58-BbNw2iDxzptco8iILPiSnLLfFn5Ps7nsRcxHaGTt3r0yqFKCuIYNnPK1vM04BXI_cfzo-HnI4I3tD6oHNHOGVQrL01MdShFQjPELPUjXM8z1qs7Kom-QyvV1iOldUN-66UuhynsmDX-CMM5TIdB-8KD_lmdhf-0DqG8JnCA20XpXyfqwS8XFkPA-t-QSjb7SdkHQFtQ4lz2PcBREFzZ2eI5j0l0Y_dQHRPYTeMwkVl1yl4MfFT4C4iso3VSF-eqaIjiFCbXKCFNyeEIW5WFsv189dhlSqU"

Dim messageId As String = "1712bc1dc22da2a2"

http.SetUrlVar("messageId",messageId)
http.SetUrlVar("attachmentId",attachmentId)

Dim url As String = "https://www.googleapis.com/gmail/v1/users/userId/messages/{$messageId}/attachments/{$attachmentId}"

' When we download, the response is JSON that contains the attachment data base64url encoded, like this:
' {
'  "size": 934,
'  "data": "JVBERi0xLjM ... CiUlRU9GCg=="
' }

Dim outputFilePath As String = "qa_output/helloWorld.pdf"

' Download into a StringBuilder.
Dim sbJson As New Chilkat.StringBuilder
success = http.DownloadSb(url,"utf-8",sbJson)
If (success = False) Then
    Debug.WriteLine(http.LastErrorText)
    Exit Sub
End If


If (http.LastStatus <> 200) Then
    ' Something failed.
    ' the JSON contains an error message.
    Debug.WriteLine(sbJson.GetAsString())
    Exit Sub
End If


' Load into a Chilkat JSON object.
Dim json As New Chilkat.JsonObject
success = json.LoadSb(sbJson)

' Extract the base64url data into a BinData.
Dim bd As New Chilkat.BinData
success = json.BytesOf("data","base64url",bd)

' Save the data to a file.
success = bd.WriteFile("qa_output/helloWorld.pdf")

Debug.WriteLine("Success.")