Creating Google Drive DriveService with existing access token - asp.net

Question

I am using ASP.NET Web API and Google.Apis.Drive.v2 Client Library for .NET to upload files to users Drive.
All examples of using the Drive Client Library for .NET require a authentication flow. But how should I create the DriveService when I already know the access token?

Answer 1

Despite the fact that have been 2 years since the question has been asked, today I've encountered the same situation and my solution is:
var valid_token = "Pass_the_valid_token_here";
var token = new Google.Apis.Auth.OAuth2.Responses.TokenResponse()
{
AccessToken = valid_token,
ExpiresInSeconds = 3600,
Issued = DateTime.Now
};
var fakeflow = new GoogleAuthorizationCodeFlow(new GoogleAuthorizationCodeFlow.Initializer
{
ClientSecrets = new ClientSecrets
{
ClientId = "fakeClientId",
ClientSecret = "fakeClientSecret"
}
});
UserCredential credential = new UserCredential(fakeflow, "fakeUserId", token);
var serviceInitializer = new BaseClientService.Initializer()
{
//ApplicationName = "Storage Sample",
HttpClientInitializer = credential
};
DriveService service = new DriveService(serviceInitializer);

Answer 2

Update
You could create your own custom token but the issue with this is going to be that the client library will not be able to refresh your access without the refresh token.
var token = new Google.Apis.Auth.OAuth2.Responses.TokenResponse()
{
AccessToken = valid_token,
ExpiresInSeconds = 3600,
Issued = DateTime.Now
};
var authorization = new GoogleAuthorizationCodeFlow(new GoogleAuthorizationCodeFlow.Initializer
{
ClientSecrets = new ClientSecrets
{
ClientId = "lientId",
ClientSecret = "ClientSecret"
}
});
var credential = new UserCredential(authorization, "user", token);
The issue you are going to have with this is that the client library is not going to be able refersh the access token after it has expired since you are not supplying a refresh token its only going to work for an hour.

Answer 3

The answer from Svetoslav Georgiev has so far worked well for me - Can't thank you enough. Google really don't help themselves with the lack of .Net (Asp Core) samples etc. Anway, one problem I did run into was that of referer restriction, so a addition/slight modification to the answer - Once you have the "service" and want to say upload a file, you need to set the referer on a buried HttpClient property...
FilesResource.CreateMediaUpload uploadRequest;
byte[] byteArray = Encoding.UTF8.GetBytes(html);
using (var stream = new MemoryStream(byteArray))
{
uploadRequest = service.Files.Create(fileMetadata, stream, "text/html");
uploadRequest.Service.HttpClient.DefaultRequestHeaders.Referrer = new Uri($"{baseUrl}");
uploadRequest.Fields = "id";
var progress = uploadRequest.Upload();
if (progress.Exception != null)
{
throw progress.Exception;
}
var file = uploadRequest.ResponseBody;
.... do what you will with file ....
}