@Html.DropDownListFor(m => m.Tbl03Regnum.Valid, new List<SelectListItem> {
     new SelectListItem { Text = SharedRes.StringsRes.ValidNo, Value = bool.FalseString },
     new SelectListItem { Text = SharedRes.StringsRes.ValidYes, Value = bool.TrueString } })

<td>@Html.DropDownListFor(m => m.Tbl03Regnum.Valid, Model.BoolValid)

public class Tbl03RegnumsFormViewModel
    {
        public List<SelectListItem> _boolValid = new  List<SelectListItem>
            {
                new SelectListItem
                    {
                        Text = "No",
                        Value = bool.FalseString
                    },
                new SelectListItem
                    {
                        Text = "Yes",
                        Value = bool.TrueString
                    }
            };

        //Properties
        public Tbl03Regnum Tbl03Regnum { get; private set; }
        public SelectList BoolValid { get; set; }                                               

        //Constructor
        public Tbl03RegnumsFormViewModel(Tbl03Regnum tbl03Regnum)
        {
            Tbl03Regnum = tbl03Regnum;
            BoolValid = new SelectList(_boolValid, Tbl03Regnum.Valid);
        }
    }

<td>@Html.DropDownListFor(m => m.Tbl03Regnum.Valid, Model._boolValid)