How to solve Google Drive API exception- "Error creating credential from JSON or JSON parameters. Unknown credential type"?

Question

I am a complete beginner to Google Cloud. My aim is to upload files to Google Drive from my .NET application (Rhino3d plugin). But I get this error related to the JSON file.

I followed the basic steps I saw in tutorials:

1. Created a project.
2. Enabled Google Drive API.
3. Created Credentials (OAuth) for "Desktop Application".
4. Downloaded the JSON file that contained Client ID and Secret.
5. Created a folder in my drive named "API_Test".
6. Used the following code to upload a file:

// Path to your JSON credentials file
string credentialsFilePath = "D:\\credentials.json";

var credential = GoogleCredential.FromFile(credentialsFilePath)
                                  .CreateScoped(DriveService.ScopeConstants.DriveFile);

var driveService = new DriveService(new BaseClientService.Initializer()
{
    HttpClientInitializer = credential
});

// Prepare the file metadata and stream
string filePath = "D:\\Points.txt";
var fileMetadata = new Google.Apis.Drive.v3.Data.File()
{
    Name = Path.GetFileName(filePath),
    Parents = new[] { "API_Test" }
};

using (var stream = new FileStream(filePath, FileMode.Open))
{
    var request = driveService.Files.Create(fileMetadata, stream, "text/plain");
    request.Fields = "id";
    request.Upload();
}                    

The error is caused at the GoogleCredential.FromFile() method. Can anyone help me with this ?

Answer 1

The file you downloaded contains the client ID and client secret that identifies your application to Google. But that does not represent a user credential which you usually need to access user owned resources, like Drive resources. And I'm sorry, I agree that the terminology is confusing.

Here's a code example on how you would obtain user credentials given the client ID and client secret.

// credentials.json points to the file containing the client ID and client secret.
var clientSecrets = await GoogleClientSecrets.FromFileAsync("D:\\credentials.json");

credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
    clientSecrets.Secrets,
    new[] { DriveService.ScopeConstants.DriveFile },
    "user",
    CancellationToken.None);

var driveService = new DriveService(new BaseClientService.Initializer()
{
    HttpClientInitializer = credential
});

You can find more documentation here:

• Using OAuth 2.0 to access Google APIs
• Using Google OAuth 2.0 .NET libraries to access Google APIs

I've filed this issue for myself to improve the error message in the case the file with the client ID and client secret is used to create a credential.