ASP.NET LISTBOX DOES NOT DISABLE
With ASP.NET 4, ListBoxes no longer disable. This appears to be a bug with ASP.NET 4
According to the ASP.NET 4 Breaking Changes whitepaper (http://www.asp.net/whitepapers/aspnet4/breaking-changes#0.1__Toc256770141)
Controls that are not designed for user input (for example, the Label control) no longer render the disabled="disabled" attribute if their Enabled property is set to false (or if they inherit this setting from a container control).
That's great for label controls etc, but a ListBox (select element with the multiple attribute) is designed for user input and should support the disabled attribute.
There are a couple of options to work around this issue.
1) extend the ListBox and override the SupportsDisabledAttribute property:
public class DisabledSupportedListBox : ListBox
{
public override bool SupportsDisabledAttribute { get { return true; } }
}
2) server side, manually add the disabled attribute:
ListBox.Attributes.Add("disabled", "disabled");
3) client side, manually add the disabled attribute:
$(function () {
$("select.aspNetDisabled").attr('disabled', 'disabled');
});
If you're already extending the ListBox, option 1 is definitely the best bet. Otherwise, I'd go with option 2 and only use option 3 as a last resort.