internal async Task <bool> RefreshTokenAsync()
        {
            try
            {
                var accounts = await Identity.GetAccountsAsync();

                var account = accounts?.FirstOrDefault();
                if (account != null)
                {
                    _AuthResult = await Identity.AcquireTokenSilentAsync(account);
                }
                return(this.IsTokenValid());
            }
            catch (Exception) { return(false); }
        }