Chatbots in C#: Writing a Smart Assistant from Scratch

Your First Chatbot in C#: From Idea to a Working Assistant

Have you ever wanted to create your own smart assistant? Not one that just replies "Hello," but a real bot that can order pizza, remind you of a meeting, or moderate a chat. The good news: you don't need to be a machine learning guru. Knowing C# and having a couple of free evenings is enough.

In this article, we will break down how to write a chatbot in C# from scratch. No magic — only clear code, proper architecture, and practical tips. You will learn how to connect to the Telegram Bot API, process commands, and build dialogues. Let's go!

Why is C# Ideal for Chatbots?

Many people think that bots are only written in Python or JavaScript. But C# is a powerful and underestimated tool for this task. Here's why:

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• Strong typing — you catch errors at compile time, not in production.
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• Async/await — a bot must handle thousands of requests simultaneously. C# handles this excellently.
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• .NET ecosystem — ready-made libraries for Telegram, Discord, Slack, and even custom protocols.
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• Performance — .NET Core / .NET 8 runs fast and consumes little memory.
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If you already write in C#, you are halfway to creating a professional chatbot. And if not, this is a great reason to start.

Planning the Architecture: So Your Bot Doesn't Break on Day One

Before writing code, let's think about how our chatbot in C# will be structured. Bad architecture is the cause of 90% of problems. The good news: for a simple bot, three components are enough:

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• API Client — communicates with the messenger (Telegram, VK, Discord).
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• Command Handler — parses messages and decides what to do.
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• Logic — the functions themselves: search, calculations, database queries.
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We will use the Chain of Responsibility pattern for handling commands. It is flexible and easy to extend. Adding a new command takes 5 minutes.

Preparation: What You Need to Install

For this work, we will need:

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• .NET SDK 8.0 or higher — download from the official website.
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• Any IDE: Visual Studio, Rider, or VS Code.
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• A Telegram account (for testing).
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Create a new project:

dotnet new console -n MyTelegramBot\ncd MyTelegramBot\ndotnet add package Telegram.Bot

The Telegram.Bot library is the most popular for C#. It fully covers the Telegram API and is actively maintained.

Getting the Bot Token

Go to Telegram, find @BotFather, and run the command /newbot. Follow the instructions. At the end, you will receive a token — a secret string like:

1234567890:ABCdefGHIjklmNOPqrstUVwxyz-1234567

Important: never publish the token publicly. Use environment variables or configuration files.

Writing the Code: Connecting to Telegram

Let's start with the simplest — a bot that replies "Hello!" to any message.

using Telegram.Bot;\nusing Telegram.Bot.Types;\nusing Telegram.Bot.Polling;\n\nvar botClient = new TelegramBotClient("YOUR_TOKEN");\n\nusing var cts = new CancellationTokenSource();\n\nvar receiverOptions = new ReceiverOptions\n{\n    AllowedUpdates = { } // receive all update types\n};\n\nbotClient.StartReceiving(\n    updateHandler: HandleUpdateAsync,\n    pollingErrorHandler: HandlePollingErrorAsync,\n    receiverOptions: receiverOptions,\n    cancellationToken: cts.Token\n);\n\nConsole.WriteLine("Bot started. Press any key to stop.");\nConsole.ReadKey