Why, if WebAPI action method returns a C# list, in Javascript / Backbone an object is received instead of an array?

Question

Situation 1

I have C# WebAPI with an action that returns a List

    [HttpGet]
    [Route("/views/documents")]
    [ValidateModelState]
    [SwaggerOperation("ViewsDocumentsGet")]
    [SwaggerResponse(statusCode: 200, type: typeof(List<Documents>), description: "...")]
    public virtual IActionResult ViewsDocumentsGet()
    {
        var result = new List<Documents>();
        ...
        return new ObjectResult(result);
    }

On the client side, there is a Backbone model, that fetches the documents

import { Model } from "backbone";
export default Model.extend({
initialize: function() {
    this._url = arguments[0];
},

url: function(strSwitch) {
    return this._url + `/views/documents`;
},

...
});

I call fetch on the model

  const response = await this.DocumentsModel.fetch();
  console.log(typeof response, response);

The console.log returns

object (14) [
0: {DocType: "...", ...}
1: {DocType: "...", ...}
2: ... 
length: 14
__proto__: Array(0)

response has type object. I am expecting array.

---

Situation 2

If I change the WebAPI action method to return an object that wraps a list, then response is an array.

    [DataContract]
    public class DocumentWrapper
    {
        ...
        [DataMember]
        public List<Document> Documents { get; set; }
        ...
    }

    [HttpGet]
    [Route("/views/documents")]
    [ValidateModelState]
    [SwaggerOperation("ViewsDocumentsGet")]
    [SwaggerResponse(statusCode: 200, type: typeof(DocumentWrapper), description: "...")]
    public virtual IActionResult ViewsDocumentsGet()
    {
        var result = new DocumentWrapper();
        ...
        return new ObjectResult(result);
    }

Now the response is still of type object, but the object has a property Documents which is an array.

object {Documents: Array(14)}
        Documents: Array(14)
        0: {DocType: "...", ...}
        1: {DocType: "...", ...}
        2: ... 
        length: 14
        __proto__: Array(0)
    __proto__: Object

---

In situation 1, I know how to convert the object to an array. But I do not want to do that. I want backbone to fetch an array from the API without me having to do any conversion.

Questions

1. Why is the C# list not automatically an array?
2. How to tell backbone to fetch an array instead of an object?

Answer 1

Backbone model fetch combines the state of the model with attributes fetched from the server by calling Backbone.sync . By default, it uses jQuery.ajax to make a RESTful JSON request and returns a jqXHR . You can override it in order to use a different persistence strategy but it will always return an jqXHR object because internally it is making ajax requests.