POST操作后，复杂模型为空

有很多关于这个问题的帖子，但我仍然找不到正确的解决方案。目前我的模型，视图和控制器是这样的:

视图:

@model Pro.Web.Models.CatDetailsView
@using (Html.BeginForm("Details", "Cat", Model, FormMethod.Post))
{
@Html.AntiForgeryToken()
@Html.ValidationSummary()

<h2>Details</h2>
<ol>
    <li>
        @Html.LabelFor(model => model.Cat.Name)
        <p>@Html.DisplayFor(model => model.Cat.Name, new { @readonly = "true" })</p>
    </li>
    <li>
        @Html.LabelFor(model => model.Cat.Owner)
        <p>@Html.DisplayFor(model => model.Cat.Owner.UserName, new { @readonly = "true" })</p>
    </li>
    <li>
        @Html.LabelFor(model => model.Cat.BornDate)
        <p>@Html.DisplayFor(model => model.Cat.BornDate, new { @readonly = "true" })</p>
    </li>
    <li>
        @Html.LabelFor(model => model.Cat.Age)
        <p>@Html.DisplayFor(model => model.Cat.Age, new { @readonly = "true" })</p>
    </li>

    <li>
        @Html.LabelFor(model => model.Cat.CatColorValue)
        <p>@Html.DisplayEnumFor(model => model.Cat.CatColorValue, typeof(Pro.Web.Models.Entities.Enums.CatColor))</p>
    </li>
    <li>
        @Html.LabelFor(model => model.Cat.Description)
        <p>@Html.DisplayFor(model => model.Cat.Description, new { @readonly = "true" })</p>
    </li>
</ol>
<input type="submit" value="Edit details" name="Command" />
}

模型:

public class CatDetailsView
{
    public Cat Cat { get; set; }
}

控制器:

[HttpPost]
    public ActionResult Details(CatDetailsView model, string Command)
    {
        if (Command.Equals("Edit details"))
        {
            Cat cat = this._catRepository.Find(model.Cat.Id);
            if (cat != null)
            {
                return RedirectToAction("Edit", "Cats", new { id = cat.Id });
            }
            else
            {
                return View(model);
            }
        }
        else
        {
            return View(model);
        }
    }

问题是控制器总是接收null的模型。我正在查看代码，但看不出有什么问题。我刚刚开始学习，所以我可能遗漏了一些微不足道的东西。我希望有人能告诉我问题出在哪里。

谢谢。