Google Oauth error: At least one client secrets (Installed or Web) should be set

Question

I'm using Google's Oauth 2.0 to upload videos to Youtube via our server. My client ID is a "service account". I downloaded the json key and added it to my solution.

Here is the relevant code:

 private async Task Run(string filePath)
        {
            UserCredential credential;
            var keyUrl = System.Web.HttpContext.Current.Server.MapPath("~/content/oauth_key.json");
            using (var stream = new FileStream(keyUrl, FileMode.Open, FileAccess.Read))
            {
                credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
                    GoogleClientSecrets.Load(stream).Secrets,
                    // This OAuth 2.0 access scope allows an application to upload files to the
                    // authenticated user's YouTube channel, but doesn't allow other types of access.
                    new[] { YouTubeService.Scope.YoutubeUpload },
                    "user",
                    CancellationToken.None
                );
            }

            var youtubeService = new YouTubeService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = credential,
                ApplicationName = Assembly.GetExecutingAssembly().GetName().Name
            });

When I run it, I get this error: At least one client secrets (Installed or Web) should be set.

However, in my json there is no "client secret":

{
  "private_key_id": "9d98c06b3e730070806dcf8227578efd0ba9989b",
  "private_key": "-----BEGIN PRIVATE KEY-----\nMIICdQIBADANBgkqhk etc,
  "client_email": "546239405652-8igo05a5m8cutggehk3rk3hspjfm3t04@developer.gserviceaccount.com",
  "client_id": "546239405652-8igo05a5m8cutggehk3rk3hspjfm3t04.apps.googleusercontent.com",
  "type": "service_account"
}

so I assume I overlooked something. Maybe I can't use the "service account" ? don't know...

Answer 1

The solution that uses json file is quite similar.

Here is sample that create VisionService using GoogleCredential object created from json file with ServiceAccountCredential.

GoogleCredential credential;
using (var stream = new FileStream(fileName, FileMode.Open, FileAccess.Read))
{
    credential = GoogleCredential.FromStream(stream)
        .CreateScoped(VisionService.Scope.CloudPlatform);
}

var service = new VisionService(new BaseClientService.Initializer()
{
    HttpClientInitializer = credential,
    ApplicationName = "my-app-name",
});

this sample require two NuGet packages:

Google.Apis.Vision.v1  
Google.Apis.Oauth2.v2