需要在 ASP.NET Core MVC 中的下拉列表中显示向下箭头

Question

正在开发 ASP.NET Core 6 MVC 应用程序。我使用选择asp-for标签助手创建了一个下拉列表。但我没有看到下拉箭头。另外我想设置默认选择的顶部或特定值。

下面是下拉列表的代码和图像

<div class="col-sm-3">             
    <select name="products" class="form-control " 
            asp-items="@(new SelectList(ViewBag.ddaircraft,"id","name"))">
    </select>
</div>

---

ViewBag 的操作方法代码：

Public IActionResult Index()
{
 var countries= _countries.getCountries();
        //add an country item on the top of list. 
        countries.Insert(0, new Aircraft { Registration="0"});

        //i used the country.name for value and item
        var ddforAircraft =  from country in countries
        select new { id = country.name, name=country.name=="0"?"Item List":country.name };

       // ddforAircraft.Append(new { id = "0", name = "" });
        ViewBag.ddaircraft = ddforAircraft;
       return View()
}

Answer 1

在小王为我指明了真正帮助我寻找答案的方向后，我找到了答案。

为了看到下拉箭头，我添加了一个 css 类“form-select”，而不删除任何内容，然后我开始看到向下箭头

 <div class="col-sm-3">             
            <select name="products" class="form-control form-select-sm form-select " asp-items="@(new SelectList(ViewBag.ddaircraft,"id","name"))">
            </select>
    </div>