Listening To Events

An event is a foundational concept in building agents — it represents something noteworthy happening either on Microsoft Teams or within your application. These events can originate from the user (e.g. installing or uninstalling your app, sending a message, submitting a form), or from your application server (e.g. startup, error in a handler).

The Teams AI Library v2 makes it easy to subscribe to these events and respond appropriately. You can register event handlers to take custom actions when specific events occur — such as logging errors, triggering workflows, or sending follow-up messages.

Here are the events that you can start building handlers for:

Event Name	Description
start	Triggered when your application starts. Useful for setup or boot-time logging.
signin	Triggered during a sign-in flow via Teams.
error	Triggered when an unhandled error occurs in your app. Great for diagnostics.
activity	A catch-all for incoming Teams activities (messages, commands, etc.).
activity.response	Triggered when your app sends a response to an activity. Useful for logging.
activity.sent	Triggered when an activity is sent (not necessarily in response).

Example 1

We can subscribe to errors that occur in the app.

app.OnError((sender, @event) =>
{
    // do something with the error
    app.Logger.Info(@event.Exception.ToString());
});

Example 2

When an activity is received, log its JSON payload.

app.OnActivity((sender, @event) =>
{
    app.Logger.Info(@event.Activity.ToString());
});