how to add print button for aspx application

The user already has a print button on their browser, you don't need to supply one.

If you want something like a print-preview then you can use css media queries to apply a print stylesheet to the page and use window.print to invoke the print dialogue

http://www.granneman.com/webdev/coding/css/printfriendlythemcvicarmet/[^]

http://www.htmlgoodies.com/beyond/javascript/article.php/3471121[^]

To pre-empt your next question, no you can't print without asking the user to confirm.

You can find the solution here
http://stackoverflow.com/questions/16033634/how-to-print-part-of-the-page-in-asp-net

Just to add my 2cents.

It's a good idea to include a print css setting. That way you can present the browser with a nicely formatted page for the user, and a second formatted for the printer (i.e. remove menus, images and links etc...)

The way to do this it to specify @Media in the css settings:

Here are a couple of articles that should explain in more detail ^_^

Print a doument with CSS[^]

Printing with Style[^]

No need to accept this. I only post as an FYI.

Good luck :)