TeamsBotTopLevelActivity.cs

using Microsoft.Bot.Builder;
using Microsoft.Bot.Connector;
using Microsoft.Bot.Connector.Authentication;
using Microsoft.Bot.Schema;
using Microsoft.Bot.Schema.Teams;
using System;
using System.Threading.Tasks;

namespace Teams.Bot.Conversations
{
    class Program
    {
        public static async Task Main(string[] args)
        {
            //Teams channel id in which to create the post.
            string teamsChannelId = "19:ba9feb7470794dbeab58e3f72ef20a6e@thread.skype";

            //The Bot Service Url needs to be dynamically fetched (and stored) from the Team. Recommendation is to capture the serviceUrl from the bot Payload and later re-use it to send proactive messages.
            string serviceUrl = "https://smba.trafficmanager.net/emea/";

            //From the Bot Channel Registration
            string botClientID = "<client-id>";
            string botClientSecret = "<client-secret>";

            MicrosoftAppCredentials.TrustServiceUrl(serviceUrl);
            var connectorClient = new ConnectorClient(new Uri(serviceUrl), new MicrosoftAppCredentials(botClientID, botClientSecret));
            var topLevelMessageActivity = MessageFactory.Text($"I am alive!");
            var conversationParameters = new ConversationParameters
            {
                IsGroup = true,
                ChannelData = new TeamsChannelData
                {
                    Channel = new ChannelInfo(teamsChannelId),
                },
                Activity = topLevelMessageActivity
            };

            await connectorClient.Conversations.CreateConversationAsync(conversationParameters);
        }
    }
}