dynamic database driven form with multiple dropdownlists,textboxes etc. - dropdownlist does not preserve its value after the page postback

Hello !

 We have a dynamic form that retrieves control information from a database and depending on the information, form put controls like dropdownlist,textbox,checkbox etc.

Few form dropdownlists:
Category
Subcategory (dependent on category selection)
Type
color (dependent on 'type' selection)

The problem is; when we select 'type' dropdownlist, it fills up color dropdownlist and empty/de-select subcategory dropdownlist that was selected previously.

We tried up Ajax toolkit as well but still the same result.

Pl ...