Upload a file to google drive using service account.

UploadController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using System.Web;
using System.Web.Mvc;
using DotNetOpenAuth.OAuth2;
using Google.Apis.Authentication;
using Google.Apis.Authentication.OAuth2.DotNetOpenAuth;
using Google.Apis.Drive.v2;
using Google.Apis.Util;
using Google.Apis.Authentication.OAuth2;
using Google.Apis.Services;
using Google.Apis.Drive.v2.Data;

namespace GoogleDriveSample.Controllers
{
    public class UploadController : Controller
    {
        private const string SERVICE_ACCOUNT_EMAIL = "****************@developer.gserviceaccount.com";

        //
        // GET: /Upload/

        public ActionResult Index()
        {
            return View();
        }

        [HttpPost]
        public ActionResult UploadFile(HttpPostedFileBase file)
        {
            using (var service = BuildService())
            {
                var gFile = new File { Title = "GoogleDriveSample.png" };
                var request = service.Files.Insert(gFile, file.InputStream, file.ContentType);
                request.Upload();
                gFile = request.ResponseBody;
            }
            return RedirectToAction("Success");
        }

        public ActionResult Success()
        {
            return View();
        }

        /// <summary>
        /// Build a Drive service object authorized with the service account.
        /// </summary>
        /// <returns>Drive service object.</returns>
        private DriveService BuildService()
        {
            var certificate = new X509Certificate2(Server.MapPath("~/App_Data/**********************************-privatekey.p12"), "notasecret",
                X509KeyStorageFlags.Exportable);

            var provider = new AssertionFlowClient(GoogleAuthenticationServer.Description, certificate)
            {
                ServiceAccountId = SERVICE_ACCOUNT_EMAIL,
                Scope = DriveService.Scopes.Drive.GetStringValue(),
            };

            var auth = new OAuth2Authenticator<AssertionFlowClient>(provider, AssertionFlowClient.GetState);

            return new DriveService((new BaseClientService.Initializer()
            {
                Authenticator = auth,
                ApplicationName = "Drive API Sample",
            }));
        }
    }
}