MVC选择列表选项组值显示在控制器上

Question

我有一个MVC4项目。我正在使用选择列表与optgroup。下面的剃刀代码，

<select name="filters" id="searchable"  multiple="multiple">
    @foreach (var item in Model.FCategories)
    {
         <optgroup label="@item.FilterCategoryName">
         @{
             var item1 = item;
         }
         @foreach (var filtre in Model.Filters.Where(m => m.FilterCategoryID == item1.FilterCategoryID))
         {
             <option value="@filtre.FilterID">@filtre.FilterName</option>
         }
         </optgroup>
    }
</select>

我的模特就像这样，

[Required(ErrorMessage = "Boş Olamaz")]
public string Name { get; set; }
[Required(ErrorMessage = "Boş Olamaz")]
public string Seo { get; set; }
public IEnumerable<Filter> Filters { get; set; }
public IEnumerable<FCategory> FCategories { get; set; }

我看到int的过滤值？但我看不到optgroup的价值....我的控制器如下所示;

public ActionResult AddToCategory()
{
    var fcat = _otherRepository.GetFCategories().ToList();
    var filter = _otherRepository.GetFilters().ToList();
    var modelim = new AdminCategoryViewModel
        {
            Filters = filter,
            FCategories = fcat
        };
    return View(modelim);       
}

[HttpPost]    
public ActionResult AddToCategory(string seo, string name,????????? filters)
{//......}

如何在控制器上显示和获取optgroup值？