Understanding ghosting, unghosting, site pages and application pages

Question

well I know definitions of these terms as mentioned:

Ghosted pages: Pages which are on file system and not on content db.

Unghosted pages : pages which are on content db.

Application Pages : normal asp.Net pages stored on file system.

site pages : Normal content pages stored in db.

According to these definitions Site pages should always be Unghosted and Application pages should always be Ghosted.

Now here comes the problem: SP virtual path provider: provides virtual path for both ghosted and unghosted site pages. How site pages be ghosted? This MSDN link also talk about ghosting and unghosting of site pages.

Could some one please explain to me these things?

Answer 1

The Ghosting/Un-Ghosting (or if you prefer the new Term Customized/Un-Customized) makes a real difference when you consider _layouts page, wcf services, etc. in the context of the SP Virtual Path provider (which then loads the Page Parser)

Example -

A Document Workspace has a default.aspx (physical) where as Team Site in SP 2010 has a Wiki Page (database). Therefore Site Pages can also be physical, until you customize any of them - via SPD.

I found the best explanations here http://msdn.microsoft.com/en-us/library/bb892189(v=office.12).aspx#WSS3Inside_Integration and http://sharepointjha.wordpress.com/2011/05/16/virtual-path-provider-in-sharepoint/ and http://sharepoint.infoyen.com/2012/03/21/site-pages-vs-application-pages/

Answer 2

Application Pages: Always ghosted

Site Pages: Ghosted and Unghosted

When site pages ghosted?

LayoutsPageBase is good example. When any page created using this base class (also called layout pages or template pages) and if it is deployed to _layout path or any other path, it has physical presence on file system (c:\program files\common files\microsoft shared\web server extensions\xx\TEMPLATE\LAYOUTS). Then VPP creates instance of page and caches it in database.

When site pages unghosted?

When VPP loads page layouts from content database (instance of page).

What VPP (Virtual Path Provider) does?

VPP does both jobs (Ghosted and Unghosted) for single request of page. First it reads template page (ghosting), second it reads instance of page (unghosting), and then combines both parties and render the page.

Example:

I have a news organization. I have created custom page layout to list down all my news. In my company, the news publisher has responsibility to generate news list page.

mycompanyListPage ----> Provisioned ----> mycompanyListPageA, mycompanyListPageB, mycompanyListPageC

Here, mycompanyListPage is PageLayout and appended A,B,C are page instances created by news publisher using mycompanyListPage template.

I use Module elements to place the template page to particular path and File element to provision instance pages. One more confusing component made MS guys is GhostableInLibrary

<File Url="mycompanyListPage.aspx" Name="mycompanyListPageA.aspx" Type="GhostableInLibrary" />

If you want to provision a page inside a document library then use above line.

<File Url="mycompanyListPage.aspx" Name="mycompanyListPageA.aspx" Type="Ghostable" />

If you want to provision a page from file system (physical path) then use above line. Its like GhostableInFileSystem.

In both the cases mycompanyListPage.aspx is ghostable and mycompanyListPageA.aspx is unghostable.

Answer 3

Take a look at this video on building custom SharePoint Site Pages. In it I explain customized/un-customized (ghosted/un-ghosted). Since Application Pages are not put into the content database they are never ghosted.

The Inside Microsoft Windows SharePoint Services 3.0 is another good source for discussion of Site and Application Pages