I have a modal popup, which has two listboxes in it and two buttons (Add and Remove). On pressing Add, a selected item is removed from the Source listbox and added to the Destination listbox, on pressing Remove, the selected item is removed from the Destination listbox and returned to the Source listbox.
I enclosed the above controls in UpdatePanel to avoid closing modal popup on pressing Add or Remove buttons. Probably, because of that UpdatePanel, I have troubles with handling the Remove button's pressing. Sometimes it works fine, but too often the selected item in the Destination listbox is said to be null (I see it when I do debugging), though it is actually selected.
Could anybody please help me deal with my problem?