Web User Control reference set to nothing when post back

[Jie]

Hi, All
I am use Web User Control for State/Province drop down list.

Public Class TEQContactCreate
Inherits TEQBasePage

Protected ddlProvinceFilter As ProvinceDropDownList

Protected ddlStateProvinceStep2 As ProvinceDropDownList

....

When the page loads, there is no problem. But when I click a button to do
the post back, ddlProvinceFilter is set to nothing, but
ddlStateProvinceStep2 is still not nothing. My page is pretty complicated.
There is 4 panels, ddlProvinceFilter is on the first panel and
ddlStateProvinceStep2 on the second panel. When I click NEXT button, first
panel is set the visible false and second panel's visible set to true. At
this time, ddlStateProvinceStep2 is also nothing.

I created a similar web project and there was no problem. Anyone knows why
it happens? Please help.

Thanks



Jie

 

[JG]

I found the problem is the outputCache on my web user control. When I
comment out this line of code, everything is OK. But I don't know why. I
would like to cache it.

<%@ OutputCache Duration="100" VaryByParam="none" %>