DropdownListFor默认值

Question

有没有一种简单的方法可以在MVC 3中为DropDownListFor添加"--Please select--"默认选项？

Answer 1

所以,我做了这样的事情:

@Html.DropDownListFor(model => model.Dessert, 
                      new SelectList(Model.AvailableDesserts, "DessertID", "DessertName"),
                      "---Select A Dessert ---")

似乎工作得很好. Dessert在我的viewmodel中是用户选择的那个. AvailableDesserts是一个可供选择的集合.希望有所帮助.

Answer 2

我在SelectList上有几个扩展方法

    public static SelectList PreAppend(this SelectList list, string dataTextField, string selectedValue, bool selected=false)
    {
        var items = new List<SelectListItem>();
        items.Add(new SelectListItem() { Selected = selected, Text = dataTextField, Value = selectedValue });
        items.AddRange(list.Items.Cast<SelectListItem>().ToList());
        return new SelectList(items, "Value", "Text");
    }
    public static SelectList Append(this SelectList list, string dataTextField, string selectedValue, bool selected=false)
    {
        var items = list.Items.Cast<SelectListItem>().ToList();
        items.Add(new SelectListItem() { Selected = selected, Text = dataTextField, Value = selectedValue });
        return new SelectList(items, "Value", "Text");
    }
    public static SelectList Default(this SelectList list,string DataTextField,string SelectedValue)
    {
        return list.PreAppend(DataTextField, SelectedValue, true);
    }

然后我的剃刀看起来像:

@Html.DropDownListFor(m=>m.SelectedState, 
    Model.StateList().Default("Select One",""))