Invalid postback or callback argument. Event validation is enabled using ''

Question

I am getting the following error when I post back a page from the client-side. I have JavaScript code that modifies an asp:ListBox on the client side.

How do we fix

Answer 1

If you fill the DropdownList through client side script then clear the list before submit the form back to server; then ASP.NET will not complain and the security will be still on.

And to get the data selected from the DDL, you can attach an "OnChange" event to the DDL to collect the value in a hidden Input or in a textbox with Style="display: none;"