Your First Chat Bot

On the previous page we got a bot token and used the getMe method to check our setup. Now, it is time to make an interactive bot that gets users' messages and replies to them like in this screenshot:

Copy the following code to Program.cs.

⚠️ Replace YOUR_BOT_TOKEN with the bot token obtained from [@BotFather].

using Telegram.Bot;
using Telegram.Bot.Types;
using Telegram.Bot.Types.Enums;

using var cts = new CancellationTokenSource();
var bot = new TelegramBotClient("YOUR_BOT_TOKEN", cancellationToken: cts.Token);
var me = await bot.GetMeAsync();
bot.OnMessage += OnMessage;

Console.WriteLine($"@{me.Username} is running... Press Enter to terminate");
Console.ReadLine();
cts.Cancel(); // stop the bot

// method that handle messages received by the bot:
async Task OnMessage(Message msg, UpdateType type)
{
    if (msg.Text is null) return;	// we only handle Text messages here
    Console.WriteLine($"Received {type} '{msg.Text}' in {msg.Chat}");
    // let's echo back received text in the chat
    await bot.SendTextMessageAsync(msg.Chat, $"{msg.From} said: {msg.Text}");
}

Run the program:

dotnet run

It runs waiting for text messages unless forcefully stopped by pressing Enter. Open a private chat with your bot in Telegram and send a text message to it. Bot should reply immediately.

By setting bot.OnMessage, the bot client starts polling Telegram servers for messages received by the bot. This is done automatically in the background, so your program continue to execute and we use Console.ReadLine() to keep it running until you press Enter.

When user sends a message, the OnMessage(...) method gets invoked with the Message object passed as an argument (and the type of update).

We check Message.Type and skip the rest if it is not a text message. Finally, we send a text message back to the same chat we got the message from.

If you take a look at the console, the program outputs the chatId numeric value.
In a private chat with you, it would be your userId, so remember it as it's useful to send yourself messages.

Received Message 'test' in Private chat with @You (123456789).