(VB.NET) Download File (Stream to Local Filesystem)

This example demonstrates how to download the content of a file from Google Drive. The file is streamed to the local filesystem.

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

Dim success As Boolean = True

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

' This example uses a previously obtained access token having permission for the 
' Google Drive scope.

Dim gAuth As New Chilkat.AuthGoogle
gAuth.AccessToken = "GOOGLE_DRIVE_ACCESS_TOKEN"

Dim rest As New Chilkat.Rest

' Connect using TLS.
' A single REST object, once connected, can be used for many Google Drive REST API calls.
' The auto-reconnect indicates that if the already-established HTTPS connection is closed,
' then it will be automatically re-established as needed.
Dim bAutoReconnect As Boolean = True
success = rest.Connect("www.googleapis.com",443,True,bAutoReconnect)

' Provide the authentication credentials (i.e. the access token)
rest.SetAuthGoogle(gAuth)

' ------------------------------------------------------------------------------
' To download a file, we must know the file ID.
' In a previous example (see Build Local Metadata Cache
' we built a local cache to make it easy to lookup file IDs given a file path.
' Let's say we want to download "testFolder/abc/123/penguins.jpg".
' First we lookup the fileId in the cache.  With the fileId, we can download the file.
Dim gdCache As New Chilkat.Cache
gdCache.Level = 0
gdCache.AddRoot("C:/ckCache/googleDrive")

Dim fileId As String = gdCache.FetchText("testFolder/abc/123/penguins.jpg")
If (gdCache.LastMethodSuccess <> True) Then
    Debug.WriteLine("Filepath not found in cache.")
    Exit Sub
End If


' We need to send a GET request like this:
' GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
' The fileId is part of the path.
Dim sbPath As New Chilkat.StringBuilder
sbPath.Append("/drive/v3/files/")
sbPath.Append(fileId)
rest.AddQueryParam("alt","media")

' Create a stream object with a SinkFile set to the path where the downloaded file will go.
Dim fileStream As New Chilkat.Stream
fileStream.SinkFile = "qa_output/penguins.jpg"
' Indicate that the response body should stream directly to fileStream,
' but only if the response status is 200.  
rest.SetResponseBodyStream(200,True,fileStream)

' Download the file, streaming the content to the SinkFile.
Dim jsonResponse As String = rest.FullRequestNoBody("GET",sbPath.GetAsString())
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' A successful response will have a status code equal to 200.
If (rest.ResponseStatusCode <> 200) Then
    Debug.WriteLine("response status code = " & rest.ResponseStatusCode)
    Debug.WriteLine("response status text = " & rest.ResponseStatusText)
    Debug.WriteLine("response header: " & rest.ResponseHeader)
    Exit Sub
End If


Debug.WriteLine("File downloaded.")