upload entire model to API via AJAX (mvc c#)

Question

I am working with Ajax, mvc and c#, uploading my model to my api action, using this information I found here: stackoverflow: How to append whole set of model to formdata and obtain it in MVC.

This is my problem When following step by step the above link, my model in the api side comes null:

//this is the conten of the viewmodel object in the api action
guid:{00000000-0000-0000-0000-000000000000}
descripcion:null
Imagen:null
Title:null

This is my viewmodel

  public class myViewModel
{
    public Guid CursoId { get; set; }
    [MaxLength(125)]
    public string Titulo { get; set; }
    public string Descripcion { get; set; }
    [Required(ErrorMessage = "select image file for course")]
    [DataType(DataType.Upload)]
    public HttpPostedFileBase Imagen { get; set; } //note this is the image
}

My web api, it is a simple action to test

 // POST: api/Test
    [Route("test")]
    public void Post([FromBody]myViewModel model)
    {//do something
    }

this is my view:

 @model ajaxtest.ViewModel.myViewModel
<form id="Editcurso" method="post" action="#" enctype="multipart/form-data">
@Html.AntiForgeryToken()
@Html.ValidationSummary(true, "Please fix the following errors.")
<div class="container">
    <div class="form-group">
        @Html.LabelFor(c => c.Titulo)
        @Html.TextBoxFor(c => c.Titulo, new { @class = "form-control" })
        @Html.ValidationMessageFor(m => m.Titulo)
    </div>
    <div class="form-group">
        @Html.LabelFor(c => c.Descripcion)
        @Html.TextAreaFor(c => c.Descripcion, new { @class = "form-control" })
        @Html.ValidationMessageFor(m => m.Descripcion)
    </div>
    <div class="form-group">
        @Html.LabelFor(m => m.Imagen)
        @Html.TextBoxFor(m => m.Imagen, new { type = "file" })
        @Html.ValidationMessageFor(m => m.Imagen)
    </div>
    <button id="submiter" type="submit" class="btn btn-primary">Listo!</button>
</div>

Here is my javascript:

  $('#Editcurso').submit(function(e) {
            e.preventDefault(); // prevent the default submit
            if (!$(this).valid()) {
                return; // exit the function and display the errors
            }


            jQuery.support.cors = true;
          // Create a formdata to pass the model, since the view was generated from viewmodel, it should contain the model.
            var model = new FormData($('#Editcurso').get(0));

            $.ajax({
                headers: {
                   'Accept': 'application/json',
                  'Content-Type': 'application/json'
                },
                url: '/api/test/test',
                type: 'post',
                dataType: 'json',
                data: JSON.stringify(model),
                processData: false,
                contentType: false,
                success: function (data) {
                    console.log(data);
                    return false;
                },
                error: function () {
                    alert('error al postear');
                    return false;
                }
            });

            e.preventDefault(); // avoid to execute the actual submit of the form.
        });

    });

What do you think is wrong and how can I fix it? thanks.