ASP.NET MVC: putting custom attributes into option

问题:

I'm using ASP.NET MVC, and am trying to render a select list with the HtmlHelper.DropDownListFor method, like so:

<%= Html.DropDownListFor(x => x.AllTopics, SelectListHelper.GetSelectListItems(Model.AllTopics), "Select a Topic", new { id = "allTopics", @class = "topic-dropdown" })%>

where SelectListHelper just returns an IList<SelectListItem> from whatever collection we're passing in. This works fine for simple things, but I want to be able to add a title attribute to each option tag (not the select list itself). But the DropDownListFor only takes in an IEnumerable<SelectListItem>, and the SelectListItem does not have anyplace that I can put in the title attribute.

Is there any way to do this without foregoing the DropDownListFor method and writing out the select list and each element by hand?

回答1:

DropDownList and derivatives don't support the functionality you're looking for. But you could also simply process the string returned by DropDownList.

<%= 
  Html.DropDownListFor(x => x.AllTopics,
    SelectListHelper.GetSelectListItems(Model.AllTopics),
    "Select a Topic", 
    new { id = "allTopics", @class = "topic-dropdown" })
  .Replace("<option", "<option attr=\"value\"")
%>

回答2:

Looking at the MVC source code, DropDownListFor uses DropDownList, which uses SelectInternal, which uses ListItemToOption, which wraps calls to TagBuilder. You could modify and include this source to accept extra calls to TagBuilder when the actual option tag is built.