sendtoTeams.cs

using System;
using System.Net.Http;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using MessageCardModel;
using System.Collections.Generic;
using System.IO;
using MessageCardModel.Actions;
using MessageCardModel.Actions.OpenUri;
using System.Threading;
using System.Collections.ObjectModel;

        public async void sendtoTeams(string summary, string title = null, string text = null, string themeColor = "0078D7", Collection<Section> sections = null, string actions = null)
        {
            settings = new JsonSerializerSettings();

            string IncomingWebhookUrl = "https://outlook.office.com/webhook/....";

            var card = new MessageCard()
            {
                Title = title,
                Originator = "Pypi TI Bot",
                Summary = summary,
                Text = text,
                ThemeColor = themeColor,
                Sections = sections,
                Actions = ParseCollection<BaseAction>(actions)
                
            };

            var converted = JsonConvert.SerializeObject(card, settings);
            var encoded = System.Text.Encoding.UTF8.GetBytes(converted);

            HttpClient client = new HttpClient();
            StringContent content = new StringContent(converted, Encoding.UTF8, "application/json");
            var response = await client.PostAsync(IncomingWebhookUrl, content);
            var responseString = await response.Content.ReadAsStringAsync();

        }