The problem is that sender.get_text() returns the original value in the dropdown, not the newly selected value. I need this to perform a check in a grid that determines if the newly selectd value exists in the grid and if it does the operation is cancelled.
How can I get the newly selected value in the dropdown ?
Hmm, this is kinda tricky, because there is OnClientSelectedIndexChanged and OnClientSelectedIndexChanging. Changed returns value after change, changing returns value before change. Maybe you can throw the original value into a hidden field on Changing, then when Changed fires you check grid, do your compare, and revert it to the value in the hidden field if it doesn't check out?