Move multiple items from one ListBox to another ListBox ASP.NET

Adding multiple items from one ListBox to another seems like a trivial thing. Lets say you want to generate a report, but you are only able to add 1 item at a time from one ListBox to another. Wouldn't that just be a waste of time?

Below is a code snippet that iterates through your first ListBox and then adds it to the second, ensuring no duplicates are being added.