Polymorphism while posting to Web Api Controller

Question

I have a Ad Model like below:

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

    public string Title { get; set; }
}

And I have lots of derived classes as well like.

public class CarAdModel : AdModel
{
    public int? Kilometer { get; set; }
}

My Web Api Controller is like:

public class AdController : ApiController
{
     [HttpPost]
     public async Task<IHttpActionResult> Post([FromBody] AdModel adModel)
     {
         //db insert
         return Ok();
     }
}

If I post a derived object like CarAdModel from my AngularJs app, I only get those properties which belong to AdModel, can I get derived object on Post action?

You don't need `[FromBody]`. Complex types are deserialized from the body automatically — Matías Fidemraizer, Sep 03 '15 at 20:17

score 1 · Answer 1 · edited Jun 03 '22 at 06:55

1

you need create custom binder for AddModel or common binder like this and some field for restore target class:

public class TypeModelBinder : DefaultModelBinder
    {
        protected override object CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType)
        {
            var typeValue = bindingContext.ValueProvider.GetValue(bindingContext.ModelName + ".ModelType");
            var type = Type.GetType((string)typeValue.ConvertTo(typeof(string)), true);
            var model = Activator.CreateInstance(type);
            bindingContext.ModelMetadata = ModelMetadataProviders.Current.GetMetadataForType(() => model, type);
            return model;
        }
    }

In my example model, the field "ModelType" contais full typename of the class

edited Jun 03 '22 at 06:55

Aage

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answered Aug 29 '15 at 19:55

vhostt

66
5

Can you please explain a little bit? – Usman Khalid Aug 30 '15 at 04:21
You override the default binder. In my case, the field "ModelType" contains the name of a class type, I recreate delivered object by classname string using Activator. you can use someelse flag – vhostt Aug 30 '15 at 07:49
Thanks a lot, this one only helped me. – Roman Sep 24 '18 at 11:34

Polymorphism while posting to Web Api Controller

1 Answers1