C# - Model is always getting its default values

Question

I have an ASP.Net Core 2.1 application.

Below is my DTO

public class Movie
{
  public int Id { get; set;}

  public bool IsSpecial {get; set;}

  public IEnumerable<Ticket> Tickets { get; set; }

    public Movie()
    {
        if(IsSpecial)
        {
            this.Tickets = new List<TicketSpecial>();
        }
        else
        {
            this.Tickets = new List<Ticket>();
        }
    }}}

Tickets (Base Class)

 public class Ticket
 {
   public int Id { get; set;}

   public string Name { get; set;}

   public decimal price { get; set;}
 } 

TicketsSpecial (Child/Derived Class)

 public class TicketsSpecial : Ticket
 {
    public string SpecialProp1 { get; set;}

    public string SpecialProp2 { get; set;}

 }

WebAPI Controller

public class MovieController : ControllerBase
{

  public IActionResult Post([FromBody]Movie movie)
  {
  }
}

Postman (HTTPPost Req payload Content-Type = application/json )

{
"IsSpecial": true,
"SpecialProp1": "Mumbai Test",
}

When I call the above API via Postman & debug at Movie ctor, it always catches the value of IsSpecial = false & all fields default value (ex. for string type null)

Thanks!

Answer 1

Change "Isspecial" to "isSpecial", same with the other property.

Another problem is that you're checking "IsSpecial" in the constructor and at this time it should be false anyway.

Answer 2

There are two issues in your current implementation. First, your request json is invalid for nested properties and json deserializer would not deserialize for you with TicketsSpecial .

Follow steps below for a workaround:

1. Movie

    public class Movie { public int Id { get; set; } public bool IsSpecial { get; set; } public IEnumerable<Ticket> Tickets { get; set; } }

2. MyJsonInputFormatter

    public class MyJsonInputFormatter: JsonInputFormatter { public MyJsonInputFormatter(ILogger logger, JsonSerializerSettings serializerSettings, ArrayPool<char> charPool, ObjectPoolProvider objectPoolProvider, MvcOptions options, MvcJsonOptions jsonOptions): base(logger, serializerSettings, charPool, objectPoolProvider, options, jsonOptions) { } public override async Task<InputFormatterResult> ReadRequestBodyAsync(InputFormatterContext context) { var result = await base.ReadRequestBodyAsync(context); if (result.Model is Movie movie && movie.IsSpecial) { context.HttpContext.Request.Body.Position = 0; string request = await new StreamReader(context.HttpContext.Request.Body).ReadToEndAsync(); var tickets = JObject.Parse(request)["Tickets"].ToObject<List<TicketSpecial>>(); movie.Tickets = tickets; } return result; } }

3. Register MyJsonInputFormatter

    services.AddMvc(o => { var serviceProvider = services.BuildServiceProvider(); var customJsonInputFormatter = new MyJsonInputFormatter( serviceProvider.GetRequiredService<ILoggerFactory>().CreateLogger<MyJsonInputFormatter>(), serviceProvider.GetRequiredService<IOptions<MvcJsonOptions>>().Value.SerializerSettings, serviceProvider.GetRequiredService<ArrayPool<char>>(), serviceProvider.GetRequiredService<ObjectPoolProvider>(), o, serviceProvider.GetRequiredService<IOptions<MvcJsonOptions>>().Value ); o.InputFormatters.Insert(0, customJsonInputFormatter); })

4. Request

    { "IsSpecial": true, "Tickets": [ {"SpecialProp1": "Mumbai Test"} ] }