C# Telegram.Bot ImBusy code to answer only if you send message with more than 10s wait

ImBusy.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Telegram.Bot;
using Telegram.Bot.Types;

namespace RateLimiter
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");

            var bot = new TelegramBotClient("1054404274:AAEzYjlN5HlOdNrrCyid34gr-yRJZOzctTk");

            bot.OnUpdate += async (sender, e) => await OnUpdate((TelegramBotClient)sender, e.Update);

            bot.StartReceiving();

            Console.ReadLine();
        }


        private static Dictionary<int, DateTime> UsersLastMessage = new Dictionary<int, DateTime>();

        private static int ToWaitSeconds = 10;

        private static async Task OnUpdate(TelegramBotClient client, Update update)
        {
            switch(update)
            {
                case { Message: { Text: {} text } message}:
                {
                    var senderId = message.From.Id;

                    if(UsersLastMessage.TryGetValue(senderId, out DateTime lastMessage))
                    {
                        if((message.Date - lastMessage).TotalSeconds < ToWaitSeconds)
                        {
                            await client.SendTextMessageAsync(
                                message.Chat.Id,
                                $"Wait {ToWaitSeconds - (message.Date - lastMessage).TotalSeconds}s");
                            return;
                        }

                        UsersLastMessage[senderId] = message.Date;
                    }
                    else
                    {
                        UsersLastMessage.Add(senderId, message.Date);
                    }

                    // Handle here ...
                    await client.SendTextMessageAsync(message.Chat.Id, "Ok.");

                    break;
                }
            }
        }
    }
}