模型:
public class Category
{
[Key]
public int ID { get; set; }
[Required(ErrorMessage = "Kategoria jest wymagana!")]
public string Kategoria { get; set; }
[Required(ErrorMessage = "Kod jest wymagany!")]
public string Kod { get; set; }
}
控制器:
public ActionResult DodajPrzedmiot()
{
if (StaticFunctions.IfLogged())
{
using (var db = new DatabaseContext())
{
var cats = from b in db.Categories
select new { b.Kategoria };
var x = cats.ToList().Select(c => new SelectListItem
{
Text = c.Kategoria,
Value = c.Kategoria
}).ToList();
//List<SelectListItem> catList = new List<SelectListItem>();
//foreach (var t in cats)
//{
// SelectListItem s = new SelectListItem();
// s.Text = t.ToString();
// s.Value = t.ToString();
// catList.Add(s);
//}
ViewBag.Kategoria = x;
}
return View();
}
else
{
return RedirectToAction("Logowanie", "User");
}
}
视图:
<div class="form-group">
@Html.LabelFor(model => model.Kategoria, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.DropDownListFor(model => model.Kategoria, null)
</div>
</div>
问题是当我添加带有选定内容的项目时,此列表显示了我从数据库中选择的值。 “ Biurowe”类别将信息添加到数据库,但同时给我错误:
类型“ System.InvalidOperationException”的异常发生在
System.Web.Mvc.dll,但未在用户代码中处理
附加信息:没有类型的ViewData项
“ IEnumerable”具有键“ Kategoria”。
我应该在这里改变什么?
最佳答案
@Html.DropDownListFor(model => model.Kategoria, null)
中的第二个参数应为项目列表,在您的情况下为ViewBag.Kategoria
。
我什至建议您使用其他名称,例如ViewBag.KategoriaList
。在ViewBag中使用与绑定到DropDownList的属性相同的列表名称时,有时会遇到问题。
试试这个代码:
public ActionResult DodajPrzedmiot()
{
if (StaticFunctions.IfLogged())
{
using (var db = new DatabaseContext())
{
var cats = from b in db.Categories
select new { b.Kategoria };
var x = cats.ToList().Select(c => new SelectListItem
{
Text = c.Kategoria,
Value = c.Kategoria
}).ToList();
ViewBag.KategoriaList = x;
}
return View();
}
else
{
return RedirectToAction("Logowanie", "User");
}
}
在视图中:
<div class="form-group">
@Html.LabelFor(model => model.Kategoria, htmlAttributes: new { @class = "control-label col-md-2" })
<div class="col-md-10">
@Html.DropDownListFor(model => model.Kategoria, ViewBag.KategoriaList as IEnumerable<SelectListItem>)
</div>
</div>
您还必须在
ViewBag
操作中填充POST
。这是您的POST
操作应为:[HttpPost]
public ActionResult DodajPrzedmiot(Item itm)
{
if (ModelState.IsValid)
{
try
{
using (var db = new DatabaseContext())
{
// try putting this code in a separate function and use that function in both actions to populate the ViewBag.
var cats = from b in db.Categories
select new { b.Kategoria };
var x = cats.ToList().Select(c => new SelectListItem
{
Text = c.Kategoria,
Value = c.Kategoria
}).ToList();
ViewBag.KategoriaList = x;
if (itm.Ilosc_zakupiona - itm.Ilosc_wypozyczona < 0) throw new ArgumentOutOfRangeException();
itm.Ilosc_magazynowa = itm.Ilosc_zakupiona - itm.Ilosc_wypozyczona;
db.Items.Add(itm);
db.SaveChanges();
}
}
catch (System.Data.Entity.Infrastructure.DbUpdateException)
{
ViewBag.ErrorMessage = "Istnieje już przedmiot o takiej nazwie i/lub kodzie!";
return View();
}
catch (ArgumentOutOfRangeException)
{
ViewBag.ErrorMessage = "Ilość zakupiona i/lub wypożyczona nie mogą być mniejsze od zera!";
return View();
}
}
return View();
}