Accessing Google Drive files with ASP.NET: Authentication issues

Other Questions Google drive
1

Hey everyone,

I’m working on an ASP.NET C# project that uses the Google Drive API. We’ve managed to upload PDFs to our Drive account, but now we’re stuck trying to download them.

When we make the API call, we get some download links. But when we try to use these links, we keep getting an ‘Unauthorized’ error. It’s weird because we can download the thumbnail, just not the actual file.

I’ve been digging through the docs and found stuff about ICredentials, but I’m lost on how to create this from our ServiceAccountCredential. I even tried setting up public access, but no luck there either.

Does anyone know how to properly authenticate these download links? I’m totally stumped here. Any help would be awesome!

Here’s a basic example of what we’re trying:

var service = new DriveService(new BaseClientService.Initializer()
{
    HttpClientInitializer = credentials,
    ApplicationName = "MyDriveApp",
});

var request = service.Files.Get(fileId);
var link = request.Execute().WebContentLink;

// This link gives 'Unauthorized' when accessed

Thanks in advance!

2

yo, i had this prob too. try using the ExportLinks property instead of WebContentLink. it worked for me. like this:

var file = service.Files.Get(fileId).Execute();
var exportLink = file.ExportLinks[“application/pdf”];

then use that exportLink with ur access token. make sure ur service account has the right permissions tho

3

I’ve been down this road before, and it can be tricky. One thing that worked for me was to use OAuth 2.0 for user authentication instead of relying solely on the ServiceAccountCredential. I set up the necessary credentials in the Google Cloud Console and then integrated the OAuth flow into my ASP.NET application. This allowed me to obtain an access token for every session, ensuring my API requests were properly authenticated. This approach resolved the unauthorized errors and improved the overall experience for both uploads and downloads. Remember to handle token refresh securely.

4

I encountered a similar issue when working with the Google Drive API in ASP.NET. The problem often stemmed from how authentication was handled for the download links.

Instead of using the WebContentLink, I used the DownloadUrl property. After obtaining the URL, I added the access token to the request headers like this:

var file = service.Files.Get(fileId).Execute();
var downloadUrl = file.DownloadUrl;

var request = (HttpWebRequest)WebRequest.Create(downloadUrl);
request.Headers.Add("Authorization", "Bearer " + credentials.Token.AccessToken);

This ensured the request was properly authenticated. Remember to manage token expiration and confirm that the service account has the necessary permissions.