Create Dynamic Dropdownlist Controls and related event

Hi,
I am creating a Dynamic Search in my application.
I create a user control and in Page_load event I create a dynamic dropdownlist and 2 dynamic button (Add,Remove)
By pressing Add button ,another row will be created with the same control (I mean another dropdown and 2 button) and so on.
and by pressing Remove button the selecetd row will be removed.

I used viewstate to keep my value for postback,

I want by changing selectedvalue of dropdownlist ,create another dynamic dropdown and textbox. so far my code is working but when I click "Add" button to create another row ,I lost my second dropdownlist and textbox.

I don not know where should I run my SelectedValue event,to keep all control on form ,by each postback I have all my control except controls that are created by selectedvalechange event

Here is all my code.

any idea???
1 using< ...