protected void CheckBoxList1_SelectedIndexChanged(object sender, EventArgs e) { ListBox1.Items.Add(CheckBoxList1.SelectedItem); } you have to add a ListItem in add method not a string! and listbox selection mode should be multiple!

vivek886 wrote: is this program right to check whether string is alpha or numeric Technically, yes, but using exceptions in such a fashion could be costly. "One man's wage rise is another man's price increase." - Harold Wilson "Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons "Man who follows car will be exhausted." - Confucius

like this[^] Panic, Chaos, Destruction. My work here is done. or "Drink. Get drunk. Fall over." - P O'H

Please read the guidelines at the top of this page. Format your message so that it is readable; what you have posted here is far too difficult to read through. You also need to identify which part of your code is failing and what you expect should be happening at that point. It's time for a new signature.