private async void InitializeApp(string authCode)
        {
            _authenticationService.AuthorizationCode = authCode;

            GetEvent <LoginEvent>().Publish(new LoginEventData
            {
                Url      = LoginUrl,
                AuthCode = authCode
            });

            var user = await OfficeService.GetUser();

            _authenticationService.UserId = user.UserPrincipalName;

            await NavigateTo("Calendar");
        }