listview pagenation

Question

i have 2 categories LIKE cat1 and Cat2 , first time page load i bind all data to list view , and after i bind to data based on category id

my problem is i put page size is 5 , and total i have 12 records ,cat1 is 7 and cat2 is 5,first time page load i show the all data ,here i got 3 page index i click on 3page index its load the recored now i am select any category like cat1 or cat2  its show the pagenation is 3pageindex and dont show the first page????