AddItemToCartTrigger.cs

[FunctionName("AddItemToCart")]
     public static async Task<ActionResult> RunAsync(
         [HttpTrigger(AuthorizationLevel.Function,  "post", Route = "cart/{id}/add")] HttpRequestMessage req,
         Guid id,
         [DurableClient] IDurableEntityClient client )
     {
         if (id == Guid.Empty)
         {
             return (ActionResult) new BadRequestObjectResult("Id is required");
         }
             var entityId = new EntityId(nameof(ShoppingCartEntity), id.ToString());
 
             var data = await req.Content.ReadAsAsync<CartItem>();
 
             await client.SignalEntityAsync<IShoppingCart>(entityId, proxy => proxy.Add(data));
 
             return (ActionResult) new AcceptedResult(); // req.CreateResponse(HttpStatusCode.Accepted);
 
     }