echo-bot.md

Echo Bot 🤖

This guide shows you how to quickly run your first bot using Visual Studio 2017 and ASP.NET Core.

Complete code is in SampleEchoBot project.

This guide assumes that

• You already have registered a bot and have its API Token.

Project Setup

Create a new ASP.NET Core (empty) version 1.1 or above app and add Telegram.Bot.Framework NuGet package to it.

Code

Bot

Create your bot class:

// EchoBot.cs
public class EchoBot : BotBase<EchoBot> {
    public EchoBot(IOptions<BotOptions<EchoBot>> botOptions)
        : base(botOptions) { }

    public override Task HandleUnknownUpdate(Update update) => Task.CompletedTask;

    public override Task HandleFaultedUpdate(Update update, Exception e) => Task.CompletedTask;
}

Update Handlers

Create an /echo command that echoes user input back:

// EchoCommand.cs
public class EchoCommandArgs : ICommandArgs {
    public string RawInput { get; set; }
    public string ArgsInput { get; set; }
}
public class EchoCommand : CommandBase<EchoCommandArgs> {
    public EchoCommand() : base(name: "echo") {}

    public override async Task<UpdateHandlingResult> HandleCommand(Update update, EchoCommandArgs args) {
        string replyText = string.IsNullOrWhiteSpace(args.ArgsInput) ? "Echo What?" : args.ArgsInput;

        await Bot.Client.SendTextMessageAsync(
            update.Message.Chat.Id,
            replyText,
            replyToMessageId: update.Message.MessageId);

        return UpdateHandlingResult.Handled;
    }
}

Pros only: Add a /start command as well that replies with text "Hello World!".

Startup

In Startup class, add the following code. This Adds Telegram bot and its update handlers to the DI container and also uses long-polling method to get new updates every 3 seconds. If you are running this app in a terminal, pressing Enter key will stop bot manager from getting updates.

// Startup.cs
private readonly IConfigurationRoot _configuration;

public Startup(IHostingEnvironment env) {
    _configuration  = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
        .Build();
}

public void ConfigureServices(IServiceCollection services) {
    services.AddTelegramBot<EchoBot>(_configuration.GetSection("EchoBot"))
        .AddUpdateHandler<EchoCommand>()
        .Configure();
}

public void Configure(IApplicationBuilder app, IHostingEnvironment env) {
    var source = new CancellationTokenSource();
    Task.Factory.StartNew(() => {
        Console.WriteLine("## Press Enter to stop bot manager...");
        Console.ReadLine();
        source.Cancel();
    });
    Task.Factory.StartNew(async () => {
        var botManager = app.ApplicationServices.GetRequiredService<IBotManager<EchoBot>>();
        while (!source.IsCancellationRequested) {
            await Task.Delay(3_000);
            await botManager.GetAndHandleNewUpdatesAsync();
        }
        Console.WriteLine("## Bot manager stopped.");
        Environment.Exit(0);
    }).ContinueWith(t => {
        if (t.IsFaulted) throw t.Exception;
    });
}

Pros only: Add the /start command you created to the list of handlers as well.

Configurations

Add the following configurations to appsettings.json file in the project's root directory.

{
  "EchoBot": {
    "ApiToken": "your bot's api token",
    "BotUserName": "your bot's username without @"
  }
}

Run

That's it! Run your the app and write to your bot: /echo Hello