How do I send a 1:1 welcome message?

I am looking to send a welcome message when a user installs my Teams bot.

I've looked at the Teams API documentation and have received mixed messages on whether this should be possible. I have read in various places that my bot should receive a conversationUpdate when the bot is installed, as well as reading in various issues that I will not receive such an event.

However, a bot exists which has this functionality. Hipmunk, when installed with private scope, sends me a message without being provoked further. How is this bot able to do this, and how can I replicate this functionality?

Thanks

Documentation likely conflicts because the MS Teams team is making very fast progress in implementing all of the botframework features. We also have made some pretty big changes to activity handlers--I'm personally not aware whether or not these specific changes made it so the bot can receive the Teams ConversationUpdate or if it works because of something else.

These tables should fairly accurately reflect the current state of activities by channel.

I just tested a Teams bot that captures every activity with a few scenarios and here's what activity handlers fire:

When A User Adds the Bot For the First Time (1:1 Welcome Message):

OnConversationUpdate
OnTurn
OnMembersAdded
OnDialog

When a Bot Is Installed to a Channel (Group Welcome Message):

Note: These should also fire when a user is added to a Team (not the channel within the team) where the bot already exists, but I'm not able to test this.

OnTurn
OnConversationUpdate
OnMembersAdded
OnDialog

When a Bot Is Messaged:

OnTurn
OnMessage
OnDialog

Here's the code I used to test this (from bot.ts, built from Echo Bot Sample):

import { ActivityHandler, MessageFactory, TurnContext } from 'botbuilder';

export class MyBot extends ActivityHandler {
    constructor() {
        super();
        // See https://aka.ms/about-bot-activity-message to learn more about the message and other activity types.
        this.onTurn(async (turnContext, next) => { await this.sendTeamsMessage('onTurn', turnContext); await next();});
        this.onMembersAdded(async (turnContext, next) => { await this.sendTeamsMessage('onMembersAdded', turnContext); await next();});
        this.onMembersRemoved(async (turnContext, next) => { await this.sendTeamsMessage('onMembersRemoved', turnContext); await next();});
        this.onEvent(async (turnContext, next) => { await this.sendTeamsMessage('onEvent', turnContext); await next();});
        this.onConversationUpdate(async (turnContext, next) => { await this.sendTeamsMessage('onConversationUpdate', turnContext); await next();});
        this.onMessage(async (turnContext, next) => { await this.sendTeamsMessage('onMessage', turnContext); await next();});
        this.onTokenResponseEvent(async (turnContext, next) => { await this.sendTeamsMessage('onTokenResponseEvent', turnContext); await next();});
        this.onUnrecognizedActivityType(async (turnContext, next) => { await this.sendTeamsMessage('onUnrecognizedActivityType', turnContext); await next();});
        this.onDialog(async (turnContext, next) => { await this.sendTeamsMessage('onDialog', turnContext); await next();});
    }

    private sendTeamsMessage = async (activityHandlerName: string, turnContext: TurnContext) => {

        const message = MessageFactory.text(`**[${activityHandlerName}]** event received`);

        await turnContext.sendActivity(message);
        console.log(`Sent: ${message.text}`)
    }
}

Note: await next() ensures that all appropriate activity handlers can be called for a given activity instead of stopping after the first one (onTurn) is called.

Sending a 1:1 Welcome Message

Something like this should work (from the Core Bot Sample):

this.onMembersAdded(async (context) => {
    const membersAdded = context.activity.membersAdded;
    for (const member of membersAdded) {
        if (member.id !== context.activity.recipient.id) {
            const welcomeCard = CardFactory.adaptiveCard(WelcomeCard);
            await context.sendActivity({ attachments: [welcomeCard] });
        }
    }
});

We're working on writing samples with the new activity handlers, but you can comb through this Samples Branch to get some ideas. I wrote mine in TypeScript, but it works and there are samples in C#, too.