C＃MVC 5 Razor：Dropdownlist显示小写值而不是大写

Question

I have an enum which looks like this (the descriptions are censored but the values are accurate):

    public enum internalTypes
    {
        [Description("Description 1 (W)")]
        W,
        [Description("Description 2 (w)")]
        w,
        [Description("Description 3 (A)")]
        A,
        [Description("Description 4 (C)")]
        C,
        [Description("Description 5 (K)")]
        K,
        [Description("Description 6 (X)")]
        X
    }

I have to display this dropdownlist in a view which gets its data from the database. For this problem, please note that the value "W" (uppercase) is the one I want to display.

The DropDownList code looks like this:

    @Html.DropDownListFor(model => model.Internal_List[i].ValueToDisplay, new SelectList(Model.listOfTypes, "Value", "Text", Model.Internal_List[i].ValueToDisplay), "", new { @class = "full", style = "width:275px" })

Model.listOfTypes:

        IEnumerable<ExtensionMethods.internalTypes> internalTypes= Enum.GetValues(typeof(ExtensionMethods.internalTypes)).Cast<ExtensionMethods.internalTypes>();
        evm.listOfTypes        = from inter in internalTypes
                                 select new SelectListItem
                                 {
                                     Text = ExtensionMethods.GetDescription(inter),
                                     Value = inter.ToString()
                                 };

Where Internal_List[i].ValueToDisplay is indeed sent correctly - that is, it correctly sends "W" (uppercase). However, the view displays "w" (lowercase):

This is a problem, because I must display "W", not "w", because that is the value that is stored in the database. Similarily, if "w" was stored, then I'd have to display "w", not "W". I don't understand why "W" is converted to "w" in this case, as when I debug my program, I can clearly see that the value being passed to the view is "W".

Would anyone be able to tell me where I may have made a mistake? Please note that I can't simply give "w" another value - I don't have a choice in the matter.

Answer 1

You cannot select the correct option using the DropDownListFor() (or the EnumDropDownListFor() etc. method). Internally the methods generate a new IEnumerable<SelectListItem> in order to set the Selected attribute based on the value of the property your binding to.

Specifically the private static IEnumerable<SelectListItem> GetSelectListWithDefaultValue() method (you can view the source code here ) compares the values using StringComparer.OrdinalIgnoreCase so a value of w (lowercase) and W (uppercase) both match and both options would be set with the selected="selected" attribute.

But because your generating a single <select> (without the multiple attribute), that would be invalid (only one option can be selected), so the browser selects only the last one that is rendered with selected="selected"

If you cannot change the values of your enum , and want to use a HtmlHelper method, you would need to write your own extension method (copy the source code into your own project, delete the various overloads you do not nee,d and make the modification so that its not case sensitive)