为什么我的SelectList不喜欢我的IList的内容？

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

IList<Person> people = GetPeopleList(); // 获取人员列表

var selectList = new SelectList(people, "Id", "Name");

@Html.DropDownListFor(model => model.SelectedPersonId, selectList, "请选择人员")

public class HomeController : Controller
{
    public ActionResult Index()
    {
        IList<Person> people = GetPeopleList(); // 获取人员列表
        var selectList = new SelectList(people, "Id", "Name");
        ViewBag.SelectList = selectList;
        return View();
    }

    private IList<Person> GetPeopleList()
    {
        // 模拟数据
        return new List<Person>
        {
            new Person { Id = 1, Name = "Alice" },
            new Person { Id = 2, Name = "Bob" },
            new Person { Id = 3, Name = "Charlie" }
        };
    }
}

@model YourNamespace.Models.HomeViewModel

@using (Html.BeginForm())
{
    @Html.DropDownListFor(model => model.SelectedPersonId, ViewBag.SelectList, "请选择人员")
    <input type="submit" value="提交" />
}