POST时模型中缺少ASP.Net MVC下拉列表数据

<select name="category">
    <option value="1">Category 1</option>
    <option value="2">Category 2</option>
    <option value="3">Category 3</option>
</select>

public ActionResult Create()
{
    List<SelectListItem> categories = new List<SelectListItem>
    {
        new SelectListItem { Value = "1", Text = "Category 1" },
        new SelectListItem { Value = "2", Text = "Category 2" },
        new SelectListItem { Value = "3", Text = "Category 3" }
    };

    ViewBag.Categories = categories;

    return View();
}

@Html.DropDownListFor(model => model.CategoryId, ViewBag.Categories as List<SelectListItem>, "Select a category")

[HttpPost]
public ActionResult Create(MyModel model)
{
    // 使用模型中的属性进行后续处理
    int selectedCategoryId = model.CategoryId;
    // 其他逻辑...

    return RedirectToAction("Index");
}