ASP.NET MVC 中的下拉列表

Question

我想创建两个下拉列表，但数据出现在一个下拉列表中，如下图所示：在此输入图像描述而另一个是空的我想要B1和B2在一个下拉列表中并在其他下拉列表中命名 zahra控制器中的此代码：// GET: Contracts/Createpublic ActionResult Create(){    var Sections = _context.Sections.ToList();    var Customers = _context.Customers.ToList();    List<SelectListItem> list = new List<SelectListItem>();    foreach (var item in Customers)    {            list.Add(new SelectListItem { Text = item.Customer_Name, Value = item.Customer_Id.ToString() });            ViewBag.Customers = list;    }    List<SelectListItem> list1 = new List<SelectListItem>();    foreach (var item in Sections)    {        list.Add(new SelectListItem { Text = item.Section_Name, Value = item.Section_Id.ToString() });        ViewBag.Sections = list1;    }    return View();}这是在视图中    <div class="form-group">        @Html.LabelFor(model => model.CustomerId, htmlAttributes: new { @class = "control-label col-md-2" })        <div class="col-md-10">            @Html.DropDownListFor(model => model.CustomerId, (IEnumerable<SelectListItem>)ViewBag.Customers, "Select customers", new { @class = "form-control" })            @Html.ValidationMessageFor(model => model.CustomerId, "", new { @class = "text-danger" })        </div>    </div>    <div class="form-group">        @Html.LabelFor(model => model.SectionsId, htmlAttributes: new { @class = "control-label col-md-2" })        <div class="col-md-10">            @Html.DropDownListFor(model => model.SectionsId, (IEnumerable<SelectListItem>)ViewBag.Sections, "Select Sections", new { @class = "form-control" })            @Html.ValidationMessageFor(model => model.SectionsId, "", new { @class = "text-danger" })        </div>    </div>

Answer 1

在第 2 个 foreach 循环中，您将添加到第 1 个列表中，而不是名为 list1 的第 2 个列表。更正如下：

    public ActionResult Create()

    {

        var Sections = _context.Sections.ToList();

        var Customers = _context.Customers.ToList();

        List<SelectListItem> list1 = new List<SelectListItem>();

        foreach (var item in Customers)

        {

            list1.Add(new SelectListItem { Text = item.Customer_Name, Value = item.Customer_Id.ToString() });

        }

        ViewBag.Customers = list1;

        List<SelectListItem> list2 = new List<SelectListItem>();

        foreach (var item in Sections)

        {

            list2.Add(new SelectListItem { Text = item.Section_Name, Value = item.Section_Id.ToString() });

        }

        ViewBag.Sections = list2;

        return View();

    }

Answer 2

问题在于您的第二个 for-each 循环，您将其添加到实际上面向客户的第一个列表中。SelectListItem

此外，简化您的 GET 方法，如下所示。它将降低复杂性。Create

// GET: Contracts/Create

[HtttpGet]

public ActionResult Create()

{

    var sections = _context.Sections.ToList();

    var customers = _context.Customers.ToList();

    ViewBag.SectionSelectList = new SelectList(sections,"Section_Id","Section_Name");

    ViewBag.CustomerSelectList = new SelectList(customers,"Customer_Id","Customer_Name");

    return View();

 }

然后在视图中将 s 替换为以下内容：@Html.DropDownListFor

@Html.DropDownListFor(model => model.CustomerId, ViewBag.CustomerSelectList, "Select customers", new { @class = "form-control" })

@Html.DropDownListFor(model => model.SectionsId, ViewBag.SectionSelectList , "Select Sections", new { @class = "form-control" })

Answer 3

试试这个：

 // GET: Contracts/Create

        public ActionResult Create()

        {

       var listOfCustomers = new List<SelectListItem>();

        foreach (var item in  _context.Customers.ToList())

        {

            listOfCustomers.Add(new SelectListItem { Text = item.Customer_Name, Value = item.Customer_Id.ToString() });

        }

        ViewBag.Customers = listOfCustomers;

        var listOfSections = new List<SelectListItem>();

            foreach (var item in  _context.Sections.ToList())

            {

                listOfSections.Add(new SelectListItem { Text = item.Section_Name, Value = item.Section_Id.ToString() });

            }

        ViewBag.Sections = listOfSections;

            return View();

        }