Invalid postback or callback argument error?

Question

I have two dropdownlists and I am filling one based on the other using javascript. In my javascript code I am calling for a webservice and with the results returned I fill t

Answer 1

If you want to modify generated controls from client side, you have to disable eventvalidation or register all possible values with RegisterForEventValidation. It's well explained here. It's because the data sent to the client and received after by the server differs.

edit:also responded here.