(VB.NET UWP/WinRT) Download Binary File to In-Memory Bytes

This example demonstrates how to download the binary content of a file from Google Drive directly into local memory.

Chilkat Universal Windows Platform (UWP) / WinRT Downloads Chilkat for the Universal Windows Platform (UWP)

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 = Await rest.ConnectAsync("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")

' To download to memory, we'll send the request in one call, then receive
' the response header, and then the response body.
' If the response header indicates failure or an unexpected response, then the
' body is not the data we desire.

' First send the HTTP request.
success = Await rest.SendReqNoBodyAsync("GET",sbPath.GetAsString())
If (success <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' Get the response header.
Dim statusCode As Integer = Await rest.ReadResponseHeaderAsync()
If (statusCode <> 200) Then
    Debug.WriteLine("response status code = " & rest.ResponseStatusCode)
    Debug.WriteLine("response status text = " & rest.ResponseStatusText)
    Debug.WriteLine("response header: " & rest.ResponseHeader)

    ' Read the response body (which should be error text or HTML)
    Dim errResponseBody As String = Await rest.ReadRespBodyStringAsync()
    If (rest.LastMethodSuccess = True) Then
        Debug.WriteLine("response body: " & errResponseBody)
    End If

    Exit Sub
End If


' Read the response body, which should contain the file data.
Dim jpgBytes() As Byte
jpgBytes = Await rest.ReadRespBodyBinaryAsync()
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' Save jpgBytes to a file so we can examine the file to verify that it worked.
Dim fac As New Chilkat.FileAccess
fac.WriteEntireFile("qa_output/penguins_out.jpg",jpgBytes)


Debug.WriteLine("File downloaded.")