Paging problem

[Verdict]

Hi
My form includes a dropdown list(DL) that represent types of customers and
submit button(BTN).
When I press the BTN it runs a query related to the selected DL and fills a
datagrid that supports pagination.

The problem is that if I go to page 15 for example and then replace my DL to
another type and submit again, if the other type doesn't have 15 pages as
well, I get error message:
Invalid CurrentPageIndex value. It must be >= 0 and < the PageCount

I tried to reset my datagrid for every BTN pressing by using :
dgSearch.CurrentPageIndex = 0

dgSearch.DataBind()

Any help is appreciated!