// ログインボタンの押下時処理
        private async void LoginButtonTapped(object sender)
        {
            var loginService         = new LoginService();
            NLC00100SIParamV2 result = null;

            try
            {
                // ログインサービスの呼び出し
                result = await loginService.LoginAsync(KaiCode.Value, UserId.Value, Password.Value, LoginDate.Value);
            }
            catch (Exception ex)
            {
                ErrorMessage.Value = ex.Message;
            }

            // ログインに成功すると認証キー'NshKey'が設定される
            if (result?.NshKey != null)
            {
                ErrorMessage.Value = string.Empty;
                await _navigationService.NavigateAsync("MenuPage");
            }
            else
            {
                ErrorMessage.Value = result.clientMessageList.FirstOrDefault().StatusMessage;
            }
        }
        public async Task <NLC00100SIParamV2> LoginAsync(string kaiCode, string userId, string password, DateTime loginDate)
        {
            var param = new NLC00100SIParamV2();

            param.KaiCode   = kaiCode;
            param.UsrID     = userId;
            param.Pswd      = password;
            param.LoginDate = loginDate;

            var task = new TaskFactory().FromAsync(client.BeginLogInV2, client.EndLogInV2, param, null);

            return(await task);
        }