O365 API Sample

CalendarAPISample.cs

using Microsoft.Office365.Exchange;
using Microsoft.Office365.OAuth;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WebApplication2
{
    public static class CalendarAPISample
    {
        const string ExchangeResourceId = "https://outlook.office365.com";
        const string ExchangeServiceRoot = "https://outlook.office365.com/ews/odata";

        
        public static async Task<IOrderedEnumerable<IEvent>> GetCalendarEvents()
        {
            var client = await EnsureClientCreated();

            // Obtain calendar event data
            var eventsResults = await (from i in client.Me.Events
                                       where i.End >= DateTimeOffset.UtcNow
                                       select i).Take(10).ExecuteAsync();

            var events = eventsResults.CurrentPage.OrderBy(e => e.Start);

            return events;
        }

        private static async Task<ExchangeClient> EnsureClientCreated()
        {
            Authenticator authenticator = new Authenticator();
            var authInfo = await authenticator.AuthenticateAsync(ExchangeResourceId);

            return new ExchangeClient(new Uri(ExchangeServiceRoot), authInfo.GetAccessToken);
        }
        public static void SignOut(Uri postLogoutRedirect)
        {
            new Authenticator().Logout(postLogoutRedirect);
        }
    }
}

HomeController.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Web;
using System.Web.Mvc;

namespace WebApplication2.Controllers
{
    public class HomeController : Controller
    {
        public async Task<ActionResult> Index()
        {
            var events = await CalendarAPISample.GetCalendarEvents();
            return View(events);
        }
    }
}

Index.cshtml

@model IEnumerable<Microsoft.Office365.Exchange.IEvent>

@{
    ViewBag.Title = "My Events";
}

<h2>My Events</h2>

 
<table class="table table-striped">
    <tr>
        <th>Subject</th>
        <th>Start</th>
    </tr>

@foreach (var item in Model) {
    <tr>
        <td>
          @item.Subject
        </td>
        <td>
            @item.Start
        </td>
    </tr>
}

</table>

Hello,
could you please let me know what's the assembly for the class Authenticator?

Thank you!!!