There's no way to apply an action filter to an area. You could write a custom exception filter attribute and then apply it as a global action filter:
public class AdminAreaHandleErrorAttribute: HandleErrorAttribute
{
public override void OnException(ExceptionContext filterContext)
{
var area = filterContext.RouteData.Values["area"] as string;
if (string.Equals(area, "Admin", StringComparison.InvariantCultureIgnoreCase))
{
base.OnException(filterContext);
}
}
}
and then register as global filter:
public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{
filters.Add(new AdminAreaHandleError());
}