Sample Telegram bot for Telegram.Bot wiki (https://github.com/TelegramBots/Telegram.Bot/wiki)

HelloBot.cs

using System;
using Telegram.Bot;
using Telegram.Bot.Args;
using Telegram.Bot.Types;
using Telegram.Bot.Types.Enums;

namespace HelloBot
{
    class Program
    {
        static readonly TelegramBotClient Bot = new TelegramBotClient("API Token");

        static void Main(string[] args)
        {
            Bot.OnMessage += Bot_OnMessage;
            Bot.StartReceiving();

            while (true) Console.ReadKey(true);
        }

        private static async void Bot_OnMessage(object sender, MessageEventArgs e)
        {
            Message message = e.Message;

            if (message.Type == MessageType.Text)
            {
                await Bot.SendTextMessageAsync(message.Chat, "Hello");
            }
        }
    }
}