(VB.NET UWP/WinRT) OneDrive -- Streaming REST Download to File

Downloads the contents of a DriveItem directly to a file in the local filesystem using the Chilkat REST class.

Note: This example requires Chilkat v9.5.0.69 or greater.

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

' Use your previously obtained access token here:
' See the following examples for getting an access token:
'    Get Microsoft Graph OAuth2 Access Token (Azure AD v2.0 Endpoint).
'    Get Microsoft Graph OAuth2 Access Token (Azure AD Endpoint).
'    Refresh Access Token (Azure AD v2.0 Endpoint).
'    Refresh Access Token (Azure AD Endpoint).


' First connect to graph.microsoft.com.  If there's a connectivity problem, we'll find out here.
Dim success As Boolean = Await rest.ConnectAsync("graph.microsoft.com",443,True,True)
If (success <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' (Make sure your token was obtained with the FilesRead or Files.ReadWrite scope.)
Dim oauth2 As New Chilkat.OAuth2
oauth2.AccessToken = "MICROSOFT_GRAPH_ACCESS_TOKEN"
rest.SetAuthOAuth2(oauth2)

' Send the GET request to download the file.
Dim uriPath As String = "/v1.0/me/drive/root:/Misc/wildlife/penguins.jpg:/content"
success = Await rest.SendReqNoBodyAsync("GET",uriPath)
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' NOTE: This way of doing the HTTP GET (i.e. download) may be more cumbersome, but it 
' allows for finer control of handling errors.  The connection establishment, the sending of the
' request, the reading of the response header, and the reading of the response body (i.e. the file data)
' are handled by separate method calls.  If the response header indicates an error, we can read
' the response body and treat it differently than if reading the file data.

' Read the response header.
Dim statusCode As Integer = Await rest.ReadResponseHeaderAsync()
Debug.WriteLine("Response Status Code = " & statusCode)
If (statusCode = 302) Then
    ' This is a redirect.  Read the response body, if any, and then follow the redirect.
    ' Usually the response body will be empty for a redirect, but we need to be sure to read
    ' the response body just in case it exists.
    Dim discard As New Chilkat.BinData
    Await rest.ReadRespBdAsync(discard)
    Await rest.DisconnectAsync(10)

    ' For OneDrive, the redirect URL does not need authorization because the only way
    ' to have obtained the direct download URL is from an authenticated request.
    ' In fact, if we leave the authentication present, the GET request to the redirect URL will fail.

    ' Note: The ClearAuth method is introduced in v9.5.0.69.
    rest.ClearAuth()

    ' Follow the redirect URL...
    Dim redirectUrl As Chilkat.Url = rest.RedirectUrl()
    Debug.WriteLine("Redirect Host: " & redirectUrl.Host)
    Debug.WriteLine("Redirect URI Path: " & redirectUrl.PathWithQueryParams)

    success = Await rest.ConnectAsync(redirectUrl.Host,redirectUrl.Port,redirectUrl.Ssl,True)
    If (success <> True) Then
        Debug.WriteLine(rest.LastErrorText)
        Exit Sub
    End If


    ' Send the request..
    success = Await rest.SendReqNoBodyAsync("GET",redirectUrl.Path)

    If (rest.LastMethodSuccess <> True) Then
        Debug.WriteLine(rest.LastErrorText)
        Exit Sub
    End If


    statusCode = Await rest.ReadResponseHeaderAsync()
    Debug.WriteLine(rest.LastErrorText)
    Debug.WriteLine("Redirect Response Status Code = " & statusCode)

End If


If (statusCode >= 300) Then

    ' Read the error response body.
    Dim sbJson As New Chilkat.StringBuilder
    success = Await rest.ReadRespSbAsync(sbJson)
    If (success <> True) Then
        Debug.WriteLine(rest.LastErrorText)
        Exit Sub
    End If


    Dim jsonErr As New Chilkat.JsonObject
    jsonErr.EmitCompact = False
    jsonErr.LoadSb(sbJson)
    Debug.WriteLine(jsonErr.Emit())

    Exit Sub
End If


' Stream the response body directly to a local file.
Dim localPath As String = "qa_output/penguins.jpg"

Dim stream As New Chilkat.Stream
stream.SinkFile = localPath

success = Await rest.ReadRespBodyStreamAsync(stream,True)
If (success <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


Debug.WriteLine("Successfully streamed a OneDrive file to the local filesystem.")