Hi Alex Rak,
I apologize for the delay in getting back to you on this. After each click on a column header element, you need to wait for the AJAX Postback to complete as seen in this article
. Once it's completed, your coded step should act against the updated grid content.
The Pages.g.vb file is dynamically generated on each run, so it's not allowed to have that file open during debugging, otherwise you'll receive the "Unable to apply this change while debugging.." error.
If you continue to have difficulty, would it be possible to provide us with the means to reproduce the issue locally(either in your app or on a public site)? If not, a Jing video
demonstrating and the issue may also help us to better understand what is happening.
the Telerik team