I found out in server side event handler
this.repeater.Items. Count() = 0
if I disable ViewState for the reapter.

So view state is needed for event handler? When I think it again, I can
understand it should be needed.

My more basic question is that: is my understanding true?
1. fresh data is get from http request parameters, and old data is get
from viewstate, and compare two to trigger some "change" event;
2.. viewstate is preserved though client hidden field, but will never be
modified in client side.
3. viewstae is updated on server side after event handler, before page
sent back to client


Thanks a lot!
Ryan