Event Out of Order Controller

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.EventGrid;
using Microsoft.Azure.EventGrid.Models;
using Microsoft.Extensions.Logging;

using System.Text.Json;

namespace order_eg.Controllers
{
    public class Item
    {
        public string Name { get; set; }

        public int Version { get; set; }

    }
    [ApiController]
    [Route("[controller]")]
    public class OrderController : ControllerBase
    {
        static private Item CurrentItem = new Item { Name = "Initial", Version = 0 };

        private readonly ILogger<OrderController> _logger;

        public OrderController(ILogger<OrderController> logger)
        {
            _logger = logger;
        }

        [HttpGet]
        public async Task<ActionResult<Item>> GetItem()
        {
            //var topicEndpoint = "https://my-entity-topic.westeurope-1.eventgrid.azure.net/api/events";
            var topicKey = "";
            var eventGridClient = new EventGridClient(new TopicCredentials(topicKey));
            var eventsList1 = CreateEvent(1);
            var eventsList2 = CreateEvent(2);

            await eventGridClient.PublishEventsAsync("my-entity-topic.westeurope-1.eventgrid.azure.net", eventsList2);
            await Task.Delay(1000);
            await eventGridClient.PublishEventsAsync("my-entity-topic.westeurope-1.eventgrid.azure.net", eventsList1);

            return Ok(CurrentItem);
        }

        private static List<EventGridEvent> CreateEvent(int inc)
        {
            var eventsList = new List<EventGridEvent>();
            eventsList.Add(new EventGridEvent()
            {
                Id = Guid.NewGuid().ToString(),
                Data = new Item()
                {
                    Name = "Test",
                    Version = CurrentItem.Version + inc
                },
                EventTime = DateTime.Now,
                EventType = "Custom",
                Subject = "MyTopic",
                DataVersion = "1.0"
            });
            return eventsList;
        }

        [HttpPost]
        public ActionResult Update(Item item)
        {
            if (item.Version == CurrentItem.Version + 1)
            {
                CurrentItem = item;
                return Ok();
            }
            throw new Exception("Out of order message"); // https://docs.microsoft.com/en-us/azure/event-grid/delivery-and-retry#failure-codes

        }

        [HttpPost("webhook")]
        public ActionResult WebHook([FromBody]EventGridEvent[] eventGridEvents)
        {
            _logger.LogInformation("Recieved {0} {1}", eventGridEvents.Length, eventGridEvents.FirstOrDefault()?.Data);

            var eventGridEvent = eventGridEvents.FirstOrDefault(); // TODO:

            if (eventGridEvent == null) return BadRequest();

            if (eventGridEvent.EventType == EventTypes.EventGridSubscriptionValidationEvent)
            {
                var element = (JsonElement)eventGridEvent.Data;
                var json = element.GetRawText();
                var data = JsonSerializer.Deserialize<SubscriptionValidationEventData>(json);
                var response = new SubscriptionValidationResponse(data.ValidationCode);
                return Ok(response);

            }
            else // TODO: event type
            {
                var element = (JsonElement)eventGridEvent.Data;
                var json = element.GetRawText();
                var data = JsonSerializer.Deserialize<Item>(json);
                return Update(data);
            }
        }
    }
}