Once your Web application has been deployed, you can easily add or update individual pieces of the application. You might want to update your Web application with new pages, images, or other functionality. Or perhaps you made changes to files that are already deployed. You can copy over the currently deployed files with new versions.
Typically, even while the application files are browsed by an end user, you can make changes without affecting the user. Users are protected because a temporary copy of the file was downloaded to the user when it was requested. The new version is available when the user refreshes the file in the Web browser. If you have a special configuration you want to use, you can find out more in Deployment of a Web Project.
Note If your application includes server components and they are in use when you make the upgrade, you might want to make the application unavailable through the Web server, otherwise the changes may generate errors. For example, if a user is browsing a page that used a .dll or .ocx files, the files for the .dll or .ocx can be locked so you can't replace it while the page is in use.
If your application uses data connections, you need to disable the data connection while you make changes to the page and then enable the connection after you are done. For more information about data connections, see Connecting to a Database.
To upgrade pages in an existing Web application
Only those pages that have been added or modified since the last deployment of the application are copied to the application root. You can then test the application on the production server.