Unable to parse JSON from Telnyx Api

Question

I am developing an endpoint in C# to accept JSON posted from an external provider (Telnyx). Here is a sample of the data:`

{
  "data": {
    "event_type": "fax.received",
    "id": "e15c28d4-147e-420b-a638-2a2647315577",
    "occurred_at": "2021-11-19T16:37:02.863682Z",
    "payload": {
      "call_duration_secs": 35,
      "connection_id": "1771912871052051547",
      "direction": "inbound",
      "fax_id": "2a168c93-3db5-424b-a408-b70a3da625bc",
      "from": "+12399999999",
      "media_url": "https://s3.amazonaws.com/faxes-prod/999",
      "page_count": 1,
      "partial_content": false,
      "status": "received",
      "to": "+12399999999",
      "user_id": "dc6e79fa-fe3b-462b-b3a7-5fb7b3111b8a"
    },
    "record_type": "event"
  },
  "meta": {
    "attempt": 1,
    "delivered_to": "https://webhook.site/27ef892c-c371-4976-ae22-22deea57080e"
  }
}

I created a class:

    public class DeserializedClass
    {
        public Data data { get; set; }
        public Meta meta { get; set; }
    }

    public class Payload
    {
        public int call_duration_secs { get; set; }
        public string connection_id { get; set; }
        public string direction { get; set; }
        public string fax_id { get; set; }
        public string from { get; set; }
        public string media_url { get; set; }
        public int page_count { get; set; }
        public bool? partial_content { get; set; }
        public string status { get; set; }
        public string to { get; set; }
        public string user_id { get; set; }
    }

    public class Data
    {
        public string event_type { get; set; }
        public string id { get; set; }
        public DateTime occurred_at { get; set; }
        public Payload payload { get; set; }
        public string record_type { get; set; }
    }

    public class Meta
    {
        public int attempt { get; set; }
        public string delivered_to { get; set; }
    }

The MVC Controller:

[HttpPost]

        public IActionResult InboundFax(DeserializedClass json)

However, any type of processing using json results in a null reference exception. Any help would be appreciated.

Answer 1

in the payload class I would change the bool? to bool or string

    public bool partial_content { get; set; }

Answer 2

Thanks for the response. I set up a test endpoint that can be accessed at https://kidsmedicalcare.com:34443/fax/InboundFax. When I post the test data that I posted earlier in this thread, I receive the error System.NullReferenceException: Object reference not set to an instance of an object.at TelnyxExamples.Controllers.FaxController.InboundFax(DeserializedClass json). The endpoint being posted to is a very simple MVC controller:

        [HttpPost]
        public IActionResult InboundFax(DeserializedClass json)
        {
            try
            {
                return Content("OK - " + json.data.event_type.ToString());
            }
            catch(Exception ex)
            {

                return Content(ex.ToString());
            }
        }

The null exception gets thrown at json.data.event_type.ToString(). I have tried other data fields as well and receive the same error message. I don't think I need to change the endpoint to a WebApi controller to accept json data. I am using Postman for the testing, but have received the same error message from the senting api (documentation for the api is https://developers.telnyx.com/docs/v2/programmable-fax/tutorials/receive-a-fax-via-api).

Answer 3

Once again, thanks for the help. I found a solution, but don't really understand why it is a solution. I changed my endpoint to a WebApi in .Net 5.0 and it now works. I thought a MVC controller could handle a JSON data model, but it appears not. Or at least the way my project was set up. Startup.cs for the non working version:

    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }
            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }