Most basic bot in MS Teams using an Outgoing Webhook to an Azure Function

TeamsSimpleBot.cs

public static class TeamsTester
{
    [FunctionName("TeamsTester")]
    public static async Task<IMessageActivity> RunAsync(
        [HttpTrigger(AuthorizationLevel.Function, "get", "post", Route = null)] 
        HttpRequest req, ILogger log)
    {
        // Get the activity passed through from the teams channel
        var requestBody = await new StreamReader(req.Body).ReadToEndAsync();
        var incomingActivity = JsonConvert.DeserializeObject<Activity>(requestBody);

        // Remove the @BotName handle to get just the command passed through
        const string pattern = @"<at>.*</at>";
        const string replacement = "";
        var command = 
            Regex.Replace(incomingActivity.Text, pattern, replacement, RegexOptions.IgnoreCase)
                .Trim();

        // Swtich through the command passed through to decide what to do and return to Teams
        AdaptiveCard response = command.ToLower() switch
        {
            "sayhello" => SayHello(incomingActivity.From.Name),
            "whoami" => WhoAmI(incomingActivity.From.Name, incomingActivity.From.AadObjectId),
            _ => Help(command)
        };

        return new Activity
        {
            Attachments = new []
            {
                new Attachment()
                {
                    ContentType = AdaptiveCard.ContentType,
                    Content = response
                }
            }
        };
    }

    private static AdaptiveCard SayHello(string name)
    {
        var card = new AdaptiveCard(new AdaptiveSchemaVersion("1.4"))
        {
            Body = new List<AdaptiveElement>()
            {
                new AdaptiveTextBlock(){Text= $"Hello {name}!"}
            }
        };
        return card;
    }

    private static AdaptiveCard WhoAmI(string name, string aadObjectId)
    {
        var card = new AdaptiveCard(new AdaptiveSchemaVersion("1.4"))
        {
            Body = new List<AdaptiveElement>()
            {
                new AdaptiveTextBlock(){Text= $"**Your name**: {name}"},
                new AdaptiveTextBlock(){Text= $"**Your Azure AD ID**: {aadObjectId}"}
            }
        };
        return card;
    }

    private static AdaptiveCard Help(string command)
    {
        var card = new AdaptiveCard(new AdaptiveSchemaVersion("1.4"))
        {
            Body = new List<AdaptiveElement>()
            {
                new AdaptiveTextBlock(){Text = $"You said {command}, which I didn't understand"},
                new AdaptiveTextBlock(){Text = "The options available are:"},
                new AdaptiveTextBlock(){Text = "**Say Hello**: This is a hello world example"},
                new AdaptiveTextBlock(){Text = "**Who Am I**: This returns your name and Azure AD ID"}
            }
        };
        return card;
    }
}