How to use SpreadsheetsService authenticated by ServiceAccountCredential?

Question

I need to use SpreadsheetsService, but I don't find the way in the official documentation .net. https://developers.google.com/google-apps/spreadsheets/?hl=ja#authorizing_requests

I have my service authenticated:

String serviceAccountEmail = "serviceAccount@developer.gserviceaccount.com";

var certificate = new X509Certificate2(@"privatekey.p12", "pass", X509KeyStorageFlags.Exportable);

ServiceAccountCredential credential = new ServiceAccountCredential(
    new ServiceAccountCredential.Initializer(serviceAccountEmail)
    {
        Scopes = new[] { DriveService.Scope.Drive }
    }.FromCertificate(certificate));

From here I can instantiate almost any service.

For example Drive Service:

var service = new DriveService(new BaseClientService.Initializer()
    {
            HttpClientInitializer = credential,
            ApplicationName = "Drive API Sample",
    });

But with SpreadsheetsService I can do this, because SpreadsheetsService wait for an string 'application name' in his default constructor or an GOAuth2RequestFactory in his property RequestFactory.

How to authenticate SpreadsheetsService with an ServiceAccountCredential?

Answer 1

Here is the answer on how to do this..... The key is to use the customHeaders on a new requestFactory

 var certificate = new
 System.Security.Cryptography.X509Certificates.X509Certificate2(p12KeyFileName,
 "notasecret", X509KeyStorageFlags.Exportable);

 string SCOPE = "https://spreadsheets.google.com/feeds
 https://docs.google.com/feeds";

 Google.Apis.Auth.OAuth2.ServiceAccountCredential credential = new
 Google.Apis.Auth.OAuth2.ServiceAccountCredential(
     new ServiceAccountCredential.Initializer(serviceAccountEmail)
     {
         Scopes = new[] { SCOPE }
     }.FromCertificate(certificate));


 bool success =
 credential.RequestAccessTokenAsync(System.Threading.CancellationToken.None).Result;

 var requestFactory = new Google.GData.Client.GDataRequestFactory("My
 Plastic SCM Service");
 requestFactory.CustomHeaders.Add(string.Format("Authorization: Bearer
 {0}", credential.Token.AccessToken));

 var s = new
 SpreadsheetsService("MySpreadsheetIntegration-v1"); s.RequestFactory =
 requestFactory; 
 return s;

Answer 2

Note that when adding the custom header you need: "Authorization: Bearer {0}" <-- with a space between "Bearer" and "{0}" Because: "Authorization: Bearer{0}" <-- no space will only get you an "unknown authorization header" Error 401 response