Expecting Items for Html DropDownFor

Question

Hi When I use the following for my dropdown

 @Html.DropDownListFor(x => x.OIC_2, new SelectList(ViewBag.StaffMembers, "Value", "Text"))

I am getting the following error even though there is data in the viewbag for staff members

Viewbag.StaffMembers is made up from

public void GetStaffMemebers() {
    List<SelectListItem> listItems = new List<SelectListItem>();
    var items = _context.StaffMember.Where(w=>w.isAcitve ==true && w.isDeleteted ==false).ToList();
    foreach (var item in items) {

            SelectListItem listItem = new SelectListItem();
            listItem.Text = item.FirstName + " " + item.LastName ;
            listItem.Value = item.Id.ToString();
            listItems.Add(listItem);
   }
        ViewBag.StaffMembers = listItems;        
}

Error

ArgumentNullException: Value cannot be null. (Parameter 'items') Microsoft.AspNetCore.Mvc.Rendering.MultiSelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, IEnumerable selectedValues, string dataGroupField) Microsoft.AspNetCore.Mvc.Rendering.SelectList..ctor(IEnumerable items, string dataValueField, string dataTextField, object selectedValue) Microsoft.AspNetCore.Mvc.Rendering.SelectList..ctor(IEnumerable items, string dataValueField, string dataTextField) CallSite.Target(Closure , CallSite , Type , object , string , string ) System.Dynamic.UpdateDelegates.UpdateAndExecute4<T0, T1, T2, T3, TRet>(CallSite site, T0 arg0, T1 arg1, T2 arg2, T3 arg3) AspNetCore.Views_MISObjects_Edit.b__27_0() in Edit.cshtml + @Html.DropDownListFor(x => x.OIC_2, new SelectList(ViewBag.StaffMembers, "Value", "Text"))

are you calling GetStaffMemebers method from controller action? — Chetan

TanvirArjel TanvirArjel · Accepted Answer · 2020-07-09T09:18:12

Better try as follows:

public void GetStaffMemebers() 
{
    var items = _context.StaffMember.Where(sm => sm.isAcitve ==true && sm.isDeleteted ==false).Select(sm => new 
    {
         Name =  sm.FirstName + " " + sm.LastName,
         Id = sm.Id.ToString()
    }).ToList();

    ViewBag.StaffMembers = items;        
}

Now make sure that GetStaffMemebers() has been called in your action method.

Then in the view as folows:

@Html.DropDownListFor(m => m.OIC_2, new SelectList(ViewBag.StaffMembers,"Id","Name"), "Select Member");

Expecting Items for Html DropDownFor

1 Answers