asp.net mvc viewdata在视图页面中显示

Question

I sent a viewdata to a view page like this.

 public ActionResult SelectRes(int id)
    {
        var ResList = resrepository.GetAll();
        ViewData["ResList"] = new SelectList(ResList, "ResId", "Res_KORNM");

        return View(svcresrelationRepository.GetAll());
    }



@foreach (var item in ViewData["ResList"] as List<ITSDapper.Dapper.Resource>)
        {
            <tr>
                <td style="text-align:center;">
                    @Html.DisplayFor(a=> item.Res_KORNM)
                </td>
            </tr>
        }

And I tried to display the viewdata in a view page but it's not worked. (Object reference not set to an instance of an object)

How display the viewdata in foreach statement?

Answer 1

You would typically use a SelectList for data that is to be selected by a user.

If this is the intention you can just use an Html.DropDownList :

@Html.DropDownList("SelectedId", 
                         (IEnumerable<SelectListItem>)ViewData["ResList"])

If you are simply needing to view the data, I would change your server-side code to use something other than a SelectList .

This could be done as follows:

Controller

 public ActionResult SelectRes(int id)
    {
        var ResList = resrepository.GetAll();

        ViewData["ResList"] = ResList;

        return View(svcresrelationRepository.GetAll());
    }

View

@foreach (var item in ViewData["ResList"] as List<ITSDapper.Dapper.Resource>)
        {
            <tr>
                <td style="text-align:center;">
                    @Html.DisplayFor(a=> item.Res_KORNM)
                </td>
            </tr>
        }

Answer 2

You are converting reference to wrong type, you are creating SelectList instance while in View you are convering it to IList<T> , you should convert it to SelectList :

@foreach (var item in ViewData["ResList"] as SelectList)
        {
            <tr>
                <td style="text-align:center;">
                    @Html.DisplayFor(a=> item.Text)  // note this as well
                </td>
            </tr>
        }