Question

I am trying to develop an HtmlHelper extension method: EnumDropDownListFor. No matter what I did I was unable to show the selected value. I tried setting Selected=true property of SelectListItem and setting selectedValue of SelectList constructor. While debugging (at return line) I can see Selected=true for the SelectLİstItem which is supposed to be Selected, for both cases. But when I “View Source” none of the options have selected=”selected” attribute.

Where am I going wrong?

Note: Toolkit is my utility class and ToByte is an extension method for Enum

    public static MvcHtmlString EnumDropDownListFor<TModel, TProperty>(
        this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression, string optionLabel = null,
        object htmlAttributes = null) where TModel : class
    {
        var selectedValue = helper.ViewData.Model == null
                                ? default(TProperty)
                                : expression.Compile()(helper.ViewData.Model);

        var enumVals = Toolkit.GetEnumValues(typeof(TProperty));

        //var selectList = from enumVal in enumVals.OfType<Enum>()
        //                 select new SelectListItem
        //                 {
        //                     Text = enumVal.GetName(),
        //                     Value = enumVal.ToByte().ToString(),
        //                     Selected = Equals(enumVal, Toolkit.To<Enum>(selectedValue))
        //                 };


        // helper.ViewData[(expression.Body as MemberExpression).Member.Name] = Toolkit.To<Enum>(selectedValue).ToByte().ToString();

        var selectList = new SelectList(from enumVal in enumVals.OfType<Enum>()
                                        select new
                                        {
                                            TextField = enumVal.GetName(),
                                            ValueField = enumVal.ToByte().ToString()
                                        }, "ValueField", "TextField", Toolkit.To<Enum>(selectedValue).ToByte().ToString());

        return helper.DropDownListFor(expression, selectList, optionLabel, htmlAttributes);
    }

Answer 1

I solved it (:
That was beacuse I am calling “helper.DropDownListFor” with same expression which returns an Enum type and I was trying to set values of options by “Byte” casted values. So it seems that Expression’s return value overrides the given selected value, makes a lot of sense.