How to create edit view with a dropdownlist

问题:

I have the following entities:

 public class Entidad
    {
        [Key]
        public int Id { get; set; }
        public string Nombre { get; set; }

        public virtual ICollection<Propiedad> Propiedades { get; set; }
}




 public class Propiedad
    {
        [Key]
        public int Id { get; set; }

        public virtual Entidad Entidad { get; set; }

        public string Codigo { get; set; }
        public string Nombre { get; set; }
        public string TipoDeDatos { get; set; }
    }

and on my edit view

 <div class="form-group">
                            @Html.LabelFor(model => model.Entidad, new { @class = "control-label col-md-2" })
                            <div class="col-md-10">
                                @Html.DropDownListFor(m => m.Entidad.Id, (SelectList)(ViewBag.EntidadList), "Seleccionar", new { @class = "form-control" })
                            </div>
                        </div>

However I get this error on the view

The ViewData item that has the key 'Entidad.Id' is of type 'System.Int32' but must be of type 'IEnumerable'. Description

my controllers are:

      // GET: /GlobalAdmin/Propiedades/Create
        public ActionResult Create()
        {
            ViewBag.EntidadList = new SelectList(db.Entidades, "id", "nombre");
            return View();
        }


   public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }


            Propiedad propiedad = db.Propiedades.Find(id);
            if (propiedad == null)
            {
                return HttpNotFound();
            }
            return View(propiedad);
        }

回答1:

You can using the following code.

In action method :

        // GET: /GlobalAdmin/Propiedades/Create
        public ActionResult Create()
        {
           ViewBag.EntidadList = 
           new SelectList(_db.Entidades.ToList().
           Select(x => new { id= x.Id, nomber= x.Nombre }), "Id", "nombre "); // Viewbag
           return View();
        }

In view page :

     <div class="form-group">
          @Html.LabelFor(model => model.Entidad, new { @class = "control-label col-md-2" })
           <div class="col-md-10">
              @Html.DropDownListFor(m => m.Entidad.Id, ViewBag.EntidadList as SelectList, "Seleccionar", new { @class = "form-control" })
          </div>
    </div>

If you want use the dropdownlist in edit view and select the item from database you can use the following code :

        // GET: /GlobalAdmin/Propiedades/Create
        public ActionResult Edit(int? id)
        {
           if (id == null)
            {
                return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
            }


        Propiedad propiedad = db.Propiedades.Find(id);
        if (propiedad == null)
         {
            return HttpNotFound();
         }
        ViewBag.EntidadList = 
           new SelectList(_db.Entidades.ToList().
           Select(x => new { id= x.Id, nomber= x.Nombre }), "Id", "nombre ",you must get id from Entidad and set here ); // Viewbag
        return View(propiedad);
        }

In edit page :

     <div class="form-group">
          @Html.LabelFor(model => model.Entidad, new { @class = "control-label col-md-2" })
           <div class="col-md-10">
              @Html.DropDownListFor(m => m.Entidad.Id, ViewBag.EntidadList as SelectList, "Seleccionar", new { @class = "form-control" })
          </div>
    </div>

I hope this help you.

回答2:

You have the wrong type for ViewBag.EntidadList, it needs to be IEnumerable<SelectListItem>. I can't see how you're building it, but as an example, you could build it like this in your controller:

var selectListItems = new List<SelectListItem>();

selectListItems.AddRange(
    someList.Select(item => new SelectListItem
    {
        Text = item.Name,
        Value = item.Id.ToString()
    }));
ViewBag.EntidadList = selectListItems;