How to ask a clarifying question to a user in the telegram api?

Question

C++ / C#

I create a bot that gives early received files. I work with api Telegram.Bot I
process the command method

private static Telegram.Bot.TelegramBotClient BOT;
{
BOT.OnMessage += BotOnMessageReceived;
}
private static async void BotOnMessageReceived(object sender, MessageEventArgs messageEventArgs)
        {
            Telegram.Bot.Types.Message msg = messageEventArgs.Message; 
            if (msg == null || msg.Type != MessageType.TextMessage) return;
            String Answer = "";
            switch (msg.Text)
            {//Стартовые команды
                case "/start": Answer = "Что я умею\n  ";break;
                case "Привет ":Answer = "Чем могу помочь?" ;break;
                case "/Document":Answer = "Выберите документ:"; Documents(msg) ; break;
                case "/Books": Answer = "Список:"; break;
                default: Answer = "Не знаю такой команды"; break;
            }
            await BOT.SendTextMessageAsync(msg.Chat.Id, Answer);
        }

After processing, the bot outputs files with the postscript /1,/2
How can I assume that Telegram.Bot.Types.Message msg has been updated?