Event Grid trigger as HTTP with validation handling

EventGridTrigger.cs

using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.Azure.WebJobs.Host;
using Newtonsoft.Json.Linq;

namespace EventGridDocs
{
    public static class HttpTrigger
    {
        [FunctionName("HttpTrigger")]
        public static async Task<HttpResponseMessage> Run([HttpTrigger(AuthorizationLevel.Function, "post")]HttpRequestMessage req, TraceWriter log)
        {
            log.Info("C# HTTP trigger function processed a request.");

            var messages = await req.Content.ReadAsAsync<JArray>();
            if (messages.Count > 0 && string.Equals((string)messages[0]["eventType"], "Microsoft.EventGrid.SubscriptionValidationEvent", System.StringComparison.OrdinalIgnoreCase))
            {
                log.Info("Validate request received");
                return req.CreateResponse<object>(new
                {
                    validationResponse = messages[0]["data"]["validationCode"]
                });
            }

            foreach (dynamic message in messages)
            {
                log.Info($"message type: {message["eventType"]}");
                log.Info($"message data: {message["data"]}");
            }

            return req.CreateResponse(HttpStatusCode.OK);
        }
    }
}