如何从中选择项目后从下拉列表中删除项目 [英] how to remove an item from the drop down list once an item has been selected from it in
问题描述
如果在asp.net mvc4中从中选择了一个项目，我怎么能从下拉列表中删除一个项目？看到流程中有会议列表和开发人员列表，您现在必须选择任何会议并向其添加开发人员，但我不能将开发人员两次添加到会议中吗？我想知道您是否可以这样做或者是否有验证？这是我的控制器：
公共类ConferenceAttendantController：Controller
{
private PrjctMngmt2Entities db = new PrjctMngmt2Entities（ ）;
//
// GET：/ ConferenceAttendants /
public ViewResult Index（）
{
var ConferenceAttendants = db.ConferenceAttendants.Include（Conference）。Include（Developer）;
返回查看（ConferenceAttendants.ToList（））;
}
//
// GET ：/ ConferenceAttendants / Create
public ActionResult Create（）
{
ViewBag.ConferenceID = new SelectList（ db.Conferences.OrderBy（d => d.Name），ConferenceID，Name）;
ViewBag.DeveloperID = new SelectList（db.Developers.Select（d => new） {d.DeveloperID，DeveloperName = d.Firs tName ++ d.LastName}）。OrderBy（d => d.DeveloperName），DeveloperID，DeveloperName）;
返回查看（）;
}
//
// POST：/ ConferenceAttendants / Create
[HttpPost]
public ActionResult Create （ConferenceAttendant ConferenceAttendant）
{
if（ModelState.IsValid）
{
db.ConferenceAttendants.Add（ ConferenceAttendant）;
db.SaveChanges（）;
返回RedirectToAction（Index，Conference）;
}
返回查看（）;
}
how can i remove remove an item from the drop down list once an item has been selected from it in asp.net mvc4? See the process is having a list of conferences and a list of developers now you must select any conference and add a developer to it but i mustnt be able to add the developer twice to the conference? I want to know whether you can do this or whether there is validation for this? This is my controller:
public class ConferenceAttendantController : Controller
{
private PrjctMngmt2Entities db = new PrjctMngmt2Entities();
//
// GET: /ConferenceAttendants/
public ViewResult Index()
{
var ConferenceAttendants = db.ConferenceAttendants.Include("Conference").Include("Developer");
return View(ConferenceAttendants.ToList());
}
//
// GET: /ConferenceAttendants/Create
public ActionResult Create()
{
ViewBag.ConferenceID = new SelectList(db.Conferences.OrderBy(d => d.Name), "ConferenceID", "Name");
ViewBag.DeveloperID = new SelectList(db.Developers.Select(d => new { d.DeveloperID, DeveloperName = d.FirstName + " " + d.LastName }).OrderBy(d => d.DeveloperName), "DeveloperID", "DeveloperName");
return View();
}
//
// POST: /ConferenceAttendants/Create
[HttpPost]
public ActionResult Create(ConferenceAttendant ConferenceAttendant)
{
if (ModelState.IsValid)
{
db.ConferenceAttendants.Add(ConferenceAttendant);
db.SaveChanges();
return RedirectToAction("Index", "Conference");
}
return View();
}
推荐答案
一般来说，你没有。用户不希望项目从下拉列表中消失，所以请不要这样做。
您可以尝试使用选中的列表框进行选择开发者。或者，更常见的是，两个列表中的>（添加）和<（删除）按钮。
Generally, you don't. Users don't expect items to disappear from a drop down list, so please don't do it that way.
You could try using a checked list box for selecting the developers. Or, the more usual, two lists with>(add) and<(remove) buttons between them.
您可以从下拉列表中删除特定的选定项目，并将数据源重新绑定到新的更新记录集。
you can remove the particular selected item from the drop down list and rebind the datasource to the new updates record set.
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