How to create a custom listener?

In TelegramBoilerplate custom listeners are inherited from Listener type.

Listeners are stored in “Listeners” folder:

Step-by-step Guide

1. Create a class named with “Listener" pattern and place it in "Listeners" folder or its subfolders:

namespace MyTelegramBot.Listeners {
    public class MessageListener : Listener {}
}

1. Add the constructor with Bot parameter:

namespace MyTelegramBot.Listeners {
    public class MessageListener : Listener
    {
        public MessageListener(Bot bot):base(bot) {}
    }
}

1. Override Validate() method where you put your listener filters:

namespace MyTelegramBot.Listeners {
    public class MessageListener : Listener
    {
        public MessageListener(Bot bot):base(bot) {}
        public override bool Validate(Context context, CancellationToken cancellationToken)
        {
            if (context.Update.Type != UpdateType.Message) // listener filters all non-message updates
                return false;
            return true;
        }
    }
}

1. Override Handler() method where you put your business logic:

namespace MyTelegramBot.Listeners {
    public class MessageListener : Listener
    {
        public MessageListener(Bot bot):base(bot) {}
        public override bool Validate(Context context, CancellationToken cancellationToken)
        {
            if (context.Update.Type != UpdateType.Message)
                return false;
            return true;
        }
        public override async Task Handler(Context context, CancellationToken cancellationToken)
        {
            // (Business logic) Listener increments message count for every call
            var session = await GetSession(context.Update.Message);
            session.Messages++;
            await SaveChanges();
        }
    }
}

1. Add the listener object to bot listeners array in /Source/Bot.cs constructor and pass this as a parameter:

        ...
        public Bot()
        {
            Listeners = new List<Listener> {
                ...
                new MessageListener(this)
                // TODO: Put more commands and other listeners.
            };
        }
        ...

1. Complete! Now you can start your bot and test your new listener!