Use refresh token in Google's People API Client Library for .NET - google-contacts-api

Question

I am rewriting an app that used Google Contacts API (RIP) to use People API. I already have a refresh token. Previously, I created an instance of the OAuth2Parameters object, and used it to create an instance of the RequestSettings class to be passed to the ContactsRequest constructor
OAuth2Parameters oparams = new OAuth2Parameters
{
AccessToken = tokenData.access_token,
RefreshToken = tokenData.refresh_token,
ClientId = ClientId,
ClientSecret = ClientSecret,
AccessType = "offline",
ApprovalPrompt = "force",
Scope = _contactScope
};
if (string.IsNullOrWhiteSpace(oparams.AccessToken))
{
oparams.AccessToken = "xyz"; //it doesn't matter what this token is, it just can't be blank, it will get refreshed
OAuthUtil.RefreshAccessToken(oparams);
dataStore._storedResponse.access_token = oparams.AccessToken;
}
var settings = new RequestSettings("My App")
{
OAuth2Parameters = oparams
};
if (paging)
{
settings.PageSize = 50;
settings.AutoPaging = true;
}
return new ContactsRequest(settings);
I cannot figure out how to do the same in the new world of People API. I obviously need to use PeopleServiceService object, but its constructor takes an instance of the Initializer object, and I don't know out how I can initialize it with the refresh token and (possibly) access token.

Answer 1

Here's the official tutorial on how to do authentication with the .NET library for all Google APIs:
https://developers.google.com/api-client-library/dotnet/guide/aaa_oauth
Here's a useful snippet from it that will also help with persisting the refresh token to a file and use it in future authentication attempts:
UserCredential credential;
using (var stream = new FileStream("client_secrets.json", FileMode.Open, FileAccess.Read))
{
credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
GoogleClientSecrets.Load(stream).Secrets,
new[] { BooksService.Scope.Books },
"user", CancellationToken.None, new FileDataStore("Books.ListMyLibrary"));
}
// Create the service.
var service = new BooksService(new BaseClientService.Initializer()
{
HttpClientInitializer = credential,
ApplicationName = "Books API Sample",
});
var bookshelves = await service.Mylibrary.Bookshelves.List().ExecuteAsync();