下拉菜单不会加载所选项目

Question

我无法使用在模型上选择的选项的下拉菜单加载编辑用户页面。当我添加用户时，它被正确保存在数据库中。

我尝试在编辑视图中绑定它，但由于某种原因它不起作用。

User.cs（模型）

public string ActivityLevel { get;放; }

控制器

    List<SelectListItem> activity = new List<SelectListItem>
    {
        new SelectListItem{ Selected = false ,Text = "Sedentary (little or no exercise)", Value = "Sedentary (little or no exercise)" },
        new SelectListItem{ Selected = false ,Text = "Lightly active (light exercise/sports 1-3 days/week)", Value = "Lightly active (light exercise/sports 1-3 days/week)"  },
        new SelectListItem{ Selected = false ,Text = "Moderately active (moderate exercise/sports 3-5 days/week)", Value = "Moderately active (moderate exercise/sports 3-5 days/week)"  },
        new SelectListItem{ Selected = false ,Text = "Very active (hard exercise/sports 6-7 days a week)", Value = "Very active (hard exercise/sports 6-7 days a week)"  },
        new SelectListItem{ Selected = false ,Text = "Extra active (very hard exercise/sports & a physical job)", Value = "Extra active (very hard exercise/sports & a physical job)"  },
    };

public ActionResult NewUser() {

        User u = new User();
        ViewBag.User = u;
        ViewBag.activity = activity;
        return View();
    }
    [HttpPost]
    public ActionResult NewUser(User user)
    {
        try
        {
            db.Users.Add(user);
            db.SaveChanges();
            return RedirectToAction("AllUsers");
        }
        catch (Exception e)
        {
            return View();
        }
    }



    public ActionResult EditUser(int id)
    {
        User user = db.Users.Find(id);
        ViewBag.User = user;


        activity.Single(i => i.Value == user.ActivityLevel).Selected = true;
        ViewBag.activity = activity;

        return View();
    }
    [HttpPut]
    public ActionResult EditUser(int id, User requestUser)
    {
        try
        {
            User user = db.Users.Find(id);
            if (TryUpdateModel(user))
            {
                user.Firstname = requestUser.Firstname;
                user.Lastname = requestUser.Lastname;
                user.Height = requestUser.Height;
                user.Weight = requestUser.Weight;
                user.Gender = requestUser.Gender;
                user.Age = requestUser.Age;
                user.Calories = requestUser.Calories;
                user.Bmr = requestUser.Bmr;
                user.ActivityLevel = requestUser.ActivityLevel;
                user.WeightChoice = requestUser.WeightChoice;
                db.SaveChanges();
            }
            return RedirectToAction("AllUsers");
        }
        catch (Exception e)
        {
            return View();
        }
    }

Edituser(View):(我觉得是这个问题，还是edit方法的get controller）

<label>Select Activity level</label>

@Html.DropDownListFor(m => m.ActivityLevel,
new SelectList(ViewBag.activity, "Value", "Text"),
new { @class = "form-control" })

新用户（查看）：

<label>Select Activity level</label>

@Html.DropDownListFor(m => m.ActivityLevel,
new SelectList(ViewBag.activity, "Value", "Text"),
new { @class = "form-control" })

Answer 1

请检查以下解决方案：请分开您的代码，在不同的 Viewbag 中传递您选择的值，例如 Viewbag.SelectedID 和传递你传入的任何内容 ViewBag.activity EditUser 和在 Edituser UI

中这样使用

@Html.DropDownListFor(m => m.ActivityLevel, new SelectList(ViewBag.activity, "Value", "Text", Viewbag.SelectedID), new { @class = "form-control" })

下拉菜单不会加载所选项目

Dropdown doesn't load on selected item

c#

asp.net-mvc

asp.net-mvc-5