public static IEnumerable <SelectListItem <bool?> > GetTrueFalseItems(string trueLabel, string falseLabel)
 {
     return(new[] { SelectListItem.Create <bool?>(true, trueLabel), SelectListItem.Create <bool?>(false, falseLabel) });
 }
 internal ListItem(SelectListItem <ItemIdType> item, bool isValid, bool isPlaceholder)
 {
     this.item          = item;
     this.isValid       = isValid;
     this.isPlaceholder = isPlaceholder;
 }