Invalid cast exception where using Enum as data source to DropDownListFor

Question

I am converting enum to IEnumerable<SelectListItem> in my controller in order to use it in DropDownListFor helper.

var roleList = EnumHelper.GetSelectList(typeof(UserRole))
           .Cast<UserRole>()
           .Except(new UserRole[] { UserRole.Admin, UserRole.Corporate })
           .Select(e => new SelectListItem { Text = e.ToString(), Value = ((int)e).ToString() });
ViewBag.SelectList = roleList;

and my razor code looks like

@Html.DropDownListFor(m => m.RoleID, (IEnumerable<SelectListItem>)ViewBag.SelectList)

but I am getting an error

System.InvalidCastException: Specified cast is not valid.

To make sure it is a valid cast I checked datatype of roleList in controller and it looks fine as shown below

during run time I ensured that ViewBag.SelectList is not null by debugging and there is no issues

but when I expand the result I get error message

Well, I guess when you tried to cast enum as int in (int)e there's the problem raised. I believe you are trying to cast abc as int there. Parse it as string and re-run — Shahjahan
– Shahjahan, Commented Oct 2, 2019 at 5:02
@Shahjahan Thanks for the comment. I tried and it still doesn't work. (int)Enum.Member gives integer value from enum. — Imad
– Imad, Commented Oct 2, 2019 at 5:23
have you tried: @Html.DropDownListFor(m => m.RoleID, ViewBag.SelectList)? — Hooman Bahreini
– Hooman Bahreini, Commented Oct 2, 2019 at 6:27

Oleksandr · Accepted Answer · 2019-10-02 11:23:37Z

1

EnumHelper.GetSelectList returns IList<SelectListItem> and then Cast<UserRole>() throws an exception because it cannot cast SelectListItem to UserRole. In order to get all enum values use Enum.GetValues

var roleList = Enum.GetValues(typeof(UserRole))
       .Cast<UserRole>()
       .Except(new UserRole[] { UserRole.Admin, UserRole.Corporate })
       .Select(e => new SelectListItem { Text = e.ToString(), Value = ((int)e).ToString() });

answered Oct 2, 2019 at 11:23

Oleksandr

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