如何在编辑模式MVC中将数据从数据库绑定到DropDownList？

Question

我想在视图中将选定值数据从模型绑定到下拉列表但仍然无法正常工作。

在下拉列表中仍然选择“选择业务单位”。

你有什么想法给我建议吗？

提前谢谢你的帮助。

这是UserModel

public class UserModel
    {

        //public static ClaimsIdentity Identity { get; set; }
        [Key]
        public Int64 UserId { get; set; }
        [Required]
        public string UserCode { get; set; }
        [Required]
        public string UserName { get; set; }
        [Required]
        public string UserEmail { get; set; }
        [Required]
        public string UserPassword { get; set; }
        [Required]
        public string UserRole { get; set; }
        [Required]
        public string UserStatus { get; set; }
        [Required]
        public DateTime LastLogin_Date { get; set; }
        [Required]
        public string Create_By { get; set; }
        [Required]
        public DateTime Create_Date { get; set; }
        [Required]
        public string Update_By { get; set; }
        [Required]
        public DateTime Update_Date { get; set; }

        public string BU_Code { get; set; }
        public virtual BusinessUnitModel BusinessUnits { get; set; }
    }

这是BusinessUnitModel

public class BusinessUnitModel
    {
        public BusinessUnitModel()
        {
            this.Users = new HashSet<UserModel>();
            this.Departments = new HashSet<DepartmentModel>();
        }

        [Key]
        public string BU_Code { get; set; }
        [Required]
        public string BU_Name { get; set; }
        [Required]
        public string BU_Prefix { get; set; }
        [Required]
        public string BU_Type { get; set; }
        [Required]
        public string BU_Status { get; set; }
        [Required]
        public string Create_By { get; set; }
        [Required]
        public DateTime Create_Date { get; set; }
        [Required]
        public string Update_By { get; set; }
        [Required]
        public DateTime Update_Date { get; set; }

        public virtual ICollection<UserModel> Users { get; set; }
        public virtual ICollection<DepartmentModel> Departments { get; set; }
        public virtual ICollection<StockModel> Stocks { get; set; }
    }

这是usercontroller

*我曾经从ViewBag更改代码.businessUnits ==> ViewBag.businessUnit *

public IActionResult Modify(Int64 id)
        {
            UserModel users = _user.GetAll(id);
            ViewBag.businessUnit = new SelectList(_businessUnit.GetAll("A").Select(x => new
            {
                Value = x.BU_Code,
                Text = x.BU_Name
            }), "Value", "Text", users.BU_Code);

            return View(users);
        }

这是用户视图

<div class="col">
@Html.LabelFor(model => model.BusinessUnits, htmlAttributes: new { @class = "control-label" })
@Html.DropDownListFor(model => model.BusinessUnits, (IEnumerable<SelectListItem>)ViewBag.businessUnit, "Select Business Unit", new { @class = "form-control" })
@Html.ValidationMessageFor(model => model.BusinessUnits)
</div>

Answer 1

ViewBag变量应该是ViewBag.businessUnit，而不是在usercontroller的Modify操作中的ViewBag.businessUnits。请参阅下面的用户控制器代码。

public IActionResult Modify(Int64 id)
        {
            UserModel users = _user.GetAll(id);
            ViewBag.businessUnit = new SelectList(_businessUnit.GetAll("A").Select(x => new
            {
                Value = x.BU_Code,
                Text = x.BU_Name
            }), "Value", "Text", users.BU_Code);

            return View(users);
        }