I am working with the Google .Net client library. The way it works is when a user wants to authenticate to Google the library spawns a new webpage for the user to authenticate
The library supports another way of authenticating for use with Web Apps.
using System;
using System.Web.Mvc;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Auth.OAuth2.Flows;
using Google.Apis.Auth.OAuth2.Mvc;
using Google.Apis.Drive.v2;
using Google.Apis.Util.Store;
namespace Google.Apis.Sample.MVC4
{
public class AppFlowMetadata : FlowMetadata
{
private static readonly IAuthorizationCodeFlow flow =
new GoogleAuthorizationCodeFlow(new GoogleAuthorizationCodeFlow.Initializer
{
ClientSecrets = new ClientSecrets
{
ClientId = "PUT_CLIENT_ID_HERE",
ClientSecret = "PUT_CLIENT_SECRET_HERE"
},
Scopes = new[] { DriveService.Scope.Drive },
DataStore = new FileDataStore("Drive.Api.Auth.Store")
});
public override string GetUserId(Controller controller)
{
// In this sample we use the session to store the user identifiers.
// That's not the best practice, because you should have a logic to identify
// a user. You might want to use "OpenID Connect".
// You can read more about the protocol in the following link:
// https://developers.google.com/accounts/docs/OAuth2Login.
var user = controller.Session["user"];
if (user == null)
{
user = Guid.NewGuid();
controller.Session["user"] = user;
}
return user.ToString();
}
public override IAuthorizationCodeFlow Flow
{
get { return flow; }
}
}
}
Code stolen from Web applications (ASP.NET MVC)