SampleAuthProvider.cs

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Security.Claims;
using System.Threading.Tasks;
using System.Web;
using Microsoft.Identity.Client;
using Microsoft.Owin.Security;
using Microsoft.Owin.Security.OpenIdConnect;
using MSGraphCalendarViewer.TokenStorage;

namespace MSGraphCalendarViewer.Helpers
{
 public sealed class SampleAuthProvider : IAuthProvider
 {
 private string redirectUri = ConfigurationManager.AppSettings["ida:RedirectUri"];
 private string appId = ConfigurationManager.AppSettings["ida:AppId"];
 private string appSecret = ConfigurationManager.AppSettings["ida:AppSecret"];
 private string scopes = ConfigurationManager.AppSettings["ida:GraphScopes"];
 private SessionTokenCache tokenCache { get; set; }

 private static readonly SampleAuthProvider instance = new SampleAuthProvider();
 private SampleAuthProvider() { }

 public static SampleAuthProvider Instance
 {
 get
 {
 return instance;
 }
 }

 public async Task<string> GetUserAccessTokenAsync()
 {
 string signedInUserID = ClaimsPrincipal.Current.FindFirst(ClaimTypes.NameIdentifier).Value;
 HttpContextWrapper httpContext = new HttpContextWrapper(HttpContext.Current);
 TokenCache userTokenCache = new SessionTokenCache(signedInUserID, httpContext).GetMsalCacheInstance();

 ConfidentialClientApplication cca = new ConfidentialClientApplication(
 appId,
 redirectUri,
 new ClientCredential(appSecret),
 userTokenCache,
 null);

 try
 {
 var accounts = await cca.GetAccountsAsync();
 AuthenticationResult result = await cca.AcquireTokenSilentAsync(scopes.Split(new char[] { ' ' }), accounts.First());
 return result.AccessToken;
 }

 catch (Exception)
 {
 HttpContext.Current.Request.GetOwinContext().Authentication.Challenge(
 new AuthenticationProperties() { RedirectUri = "/" },
 OpenIdConnectAuthenticationDefaults.AuthenticationType);

 throw new Exception();
 }
 }
 }
}