very weird method in partial class not listed in intellisense

I have created partial class for winform many times with no problem. When doing the same thing in asp.net I am stucked even with the most basic sample code:


Default.partial.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
< ...