Display confirmation from code behind before continuing a process in ASP.NET (part one)

I noticed that many developers asked this question or similar: After a user clicks a button on a page, my application performs some check, then prompts user for confirmation, then based on user’s response, my application will either continue the process or cancel the process. How can I accomplish this?

I wrote an article on Experts-Exchange.com regarding this question and here is the link to it:

Display confirmation from code behind before continuing a process in ASP.NET (part one)