Advantages of Master Pages
Master pages provide functionality that developers have traditionally created by copying existing code, text, and control elements repeatedly; using framesets; using include files for common elements; using ASP.NET user controls; and so on. Advantages of master pages include the following:
- They allow you to centralize the common functionality of your pages so that you can make updates in just one place.
- They make it easy to create one set of controls and code and apply the results to a set of pages. For example, you can use controls on the master page to create a menu that applies to all pages.
- They give you fine-grained control over the layout of the final page by allowing you to control how the placeholder controls are rendered.
- They provide an object model that allows you to customize the master page from individual content pages.
Run-time Behavior of Master Pages
At run time, master pages are handled in the following sequence:
- Users request a page by typing the URL of the content page.
- When the page is fetched, the @ Page directive is read. If the directive references a master page, the master page is read as well. If this is the first time the pages have been requested, both pages are compiled.
- The master page with the updated content is merged into the control tree of the content page.
- The content of individual Content controls is merged into the corresponding ContentPlaceHolder control in the master page.
- The resulting merged page is rendered to the browser.