验证模态形式

I am trying to popup a form so user fill it then I save that record. If data is wrong I want to inform the user just a classic validation issue.

I am trying this code but when model is not valid it show the mistake but literally it only returns what is in the partial view, it is not loading my layout nor my modal form, all I get is a white page just with my partial.

so what am I doing wrong?

This is my modal form:

And after validation all I get is this:

Code: Model:

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

    [Required]
    [StringLength(50, MinimumLength = 6)]
    public string Model { get; set; }
    public string Brand { get; set; }
    public string Year { get; set; }
    public string Color { get; set; }
}

View:

<!-- Modal -->
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
<div class="modal-dialog">
    <div class="modal-content">
        <div class="modal-header">
            <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
            <h4 class="modal-title" id="myModalLabel">Add Car</h4>
        </div>
        <div class="modal-body">
            @Html.Partial("CreatePartialView",new Car())
        </div>
        <div class="modal-footer">
            <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
            <button type="button" class="btn btn-primary" id="savechanges">Save changes</button>
        </div>
    </div><!-- /.modal-content -->
</div><!-- /.modal-dialog -->

my partial:

@model ControliBootstrap.Models.Car

@using (Ajax.BeginForm("ModalAdd", "Cars",new AjaxOptions()
{
UpdateTargetId = "mymodalform"
}))
{
<div class="form-horizontal" id="mymodalform">
    @Html.ValidationSummary(true)

    <div class="form-group">
        @Html.LabelFor(model => model.Model, new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.Model)
            @Html.ValidationMessageFor(model => model.Model)
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.Brand, new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.Brand)
            @Html.ValidationMessageFor(model => model.Brand)
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.Year, new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.Year)
            @Html.ValidationMessageFor(model => model.Year)
        </div>
    </div>

    <div class="form-group">
        @Html.LabelFor(model => model.Color, new { @class = "control-label col-md-2" })
        <div class="col-md-10">
            @Html.EditorFor(model => model.Color)
            @Html.ValidationMessageFor(model => model.Color)
        </div>
    </div>

    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Create" class="btn btn-default" />
        </div>
    </div>
</div>
}

and finlly my controler:

 public ActionResult ModalAdd(Car car)
    {
        if (ModelState.IsValid)
        {
            db.Cars.Add(car);
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        return PartialView("CreatePartialView",car);
    }  

Don't forget to include jQuery Unobtrusive AJAX - it's the library that makes normal HTML forms have some AJAX capabilities.