Need C# code to display an Alert box on button click

Every time you write that code, it will run, that seems obvious. So, write the code only when the save button is pushed ( in the click event ). If that's not obvious to you, you should stop what you're doing ( which smells like real work ) and learn the absolute basics of programming, the stuff we in the west learned in the first week of the four year course we took before we started asking people to pay for our efforts.

Oh, I think I get it now. You save on a button click that does other things, too ? Well, that doesn't seem like great UI to me, but, in that case, you should in general be checking if the value was changed before saving it, and then only show the message if that was the case. It still sounds to me like what is happening is perfectly logical, and you need to break down the steps of your design to see when you want the message, when you do not, and how to write code to tell the difference. It's also bad to be saving when you don't need to, because unless it's a low use site, you should be more frugal with resources like database access.

One other thing - I doubt it applies here, but everyone is having a hard time decoding your question, so I throw it out there for what it's worth. You can use the OnClientClick method to run javascript BEFORE the postback. So you can use that to show a message box before a postback, or return false to stop the postback occuring.