Basket ID creating on every drop drown or button event

Question

Hi,

 

My website is build in asp.net c# 

i have a webpage where we select some options from drop downlist and those list are also iconnected with each other ().#

# on every button event or dropdown slecect its creating new basket ID

and when i click on continue button it not passing to new page for payment.

because id is different 

#please help me to solve it