internal static async Task ContinueAcquireTokenAsync(WebAuthenticationBrokerContinuationEventArgs args)
        {
            _authenticationResult = await _authenticationContext.ContinueAcquireTokenAsync(args);

            // TODO by app developer: ideally we want to preserve the state of what we wanted to do before the continuation call, and do it.
            // see https://msdn.microsoft.com/library/windows/apps/dn631755.aspx and http://www.cloudidentity.com/blog/2014/06/16/adal-for-windows-phone-8-1-deep-dive/
        }
        public async Task ContinueAcquireToken(IWebAuthenticationBrokerContinuationEventArgs args)
        {
            var result = await authContext.ContinueAcquireTokenAsync(args);

            acquireTokenTcs.SetResult(Convert(result));
        }
 // This method is automatically invoked when the application is reactivated after an authentication interaction through WebAuthenticationBroker.
 public async void ContinueWebAuthentication(WebAuthenticationBrokerContinuationEventArgs args)
 {
     // pass the authentication interaction results to ADAL, which will conclude the token acquisition operation and invoke the callback specified in AcquireTokenAndContinue.
     await authContext.ContinueAcquireTokenAsync(args);
 }