如何更改下拉内容

Question

我正在尝试在 ASP.NET MVC 中执行下拉筛选内容。我希望下拉列表显示三种毕业状态（已毕业、通过、未通过），当我选择一个时，它只会显示所选状态的学生！控制器：ViewBag.GraduationStatus = new SelectList(db.Graduated_Students, "Graduated Status");var graduates = db.Graduated_Students.Where(student => student.GraduationStatus != null);return View(graduates.ToList());看法：@using (Html.BeginForm()){    <table>        <tr>            <th>                @Html.DropDownList("GraduationStatus", null, htmlAttributes: new { @class = "form-control" })            </th>            <th>                <input type="submit" value="Filter by graduation Status" />            </th>        </tr>    </table>}模型 ：namespace CodeboxxSchoolPortal{    using System;    using System.ComponentModel.DataAnnotations;    using System.Collections.Generic;    public partial class Graduated_Students    {        public int ID { get; set; }        public int CohortId { get; set; }        public string GraduationStatus { get; set; }        public string Name { get; set; }        public string FirstName { get; set; }        public string LastName { get; set; }        public string ContractStatus { get; set; }        public string DepositStatus { get; set; }        public Nullable<int> PartnerId { get; set; }        public string PartnerName { get; set; }            public List<SelectListItem> GraduationStatusList = new List<SelectListItem>            {                 new SelectListItem { Value="Graduated", Text="Graduated" },                 new SelectListItem { Value ="Pass", Text="Pass" },                 new SelectListItem { Value ="Failed", Text="Failed" }            };        public class SelectListItem        {            public string Value { get; set; }            public string Text { get; set; }        }    }}

Answer 1

这是我认为你应该做的，

如果您Action在控制器中是GetStudents，并且您的下拉列表的值为字符串（毕业状态），请将其传递给过滤器按钮上的控制器单击

 [HttpPost]

 public ActionResult Documents(string? graduationStatus)

 {

     var graduates = db.Graduated_Students.Where(student => student.GraduationStatus == graduationStatus);

     return View(graduates.ToList());

 }

请注意，必须与数据库中的string? graduationStatus类型相同student.GraduationStatus

还要确保Html.BeginForm()对控制器有正确的操作

@Html.BeginForm("GetStudents", "Controller", FormMethod.Post, new { @class = "my_form"})

编辑：

将下面的行更改为

@Html.DropDownList("GraduationStatus", new SelectList(ViewBag.GraduationStatus, "Value Here", "Text Here", null), "- Select -", new { @class = "form-control"})