DropDownListFor 不尊重 SelectList 的 Selected 属性

根据 DropDownListFor 不尊重 SelectList 的 Selected 属性，我们将探讨在ASP.NET MVC开发中遇到的一个问题，并提供解决方案。在ASP.NET MVC中，DropDownListFor是一个常用的HTML辅助函数，用于生成下拉列表。它接受一个SelectList对象作为参数，以提供下拉列表的选项。然而，我们发现DropDownListFor在处理SelectList的Selected属性时存在一个问题。

csharp
var options = new List
{
    new SelectListItem { Value = "1", Text = "选项1", Selected = true },
    new SelectListItem { Value = "2", Text = "选项2" },
    new SelectListItem { Value = "3", Text = "选项3" }
};
var selectList = new SelectList(options, "Value", "Text");

csharp
@Html.DropDownListFor(model => model.SelectedValue, selectList)

csharp
public class HomeController : Controller
{
    public ActionResult Index()
    {
        var options = new List
        {
            new SelectListItem { Value = "1", Text = "选项1", Selected = true },
            new SelectListItem { Value = "2", Text = "选项2" },
            new SelectListItem { Value = "3", Text = "选项3" }
        };
        var selectList = new SelectList(options, "Value", "Text");
        var model = new MyModel
        {
            SelectedValue = "2",
            SelectList = selectList
        };
        return View(model);
    }
}

csharp
@model MyModel
@{
    ViewBag.Title = "DropDownListFor问题解决方案";
}
DropDownListFor问题解决方案
@Html.DropDownListFor(model => model.SelectedValue, Model.SelectList)