Relative URLs in SharePoint
If you are referencing resources such as style sheets, images, JavaScript etc in a SharePoint environment you need to be careful to ensure that URLs are relative to the current site (or site collection) so that if sites are moved the references don’t break. For example if you are referencing a style sheet from a master page in a publishing site you will probably want the link to be relative to the site collection so that sites below the root still reference the style sheets at the top level.
In code you can get a reference to the current site or site collection using SPContext.Current.Web.ServerRelativeUrl (site) or SPContext.Current.Site.ServerRelativeUrl (site collection).
You can also do this in your master pages, page layouts or other pages on the site by using the SPUrl expression prefix provided by the Microsoft.SharePoint.Publishing.WebControls.SPUrlExpressionBuilder class. Examples are shown below:
<link rel="stylesheet" type="text/css" href="<% $SPUrl:~SiteCollection/Style Library/Provoke/main.css %>" runat="server">
<link rel="stylesheet" type="text/css" href="<% $SPUrl:~Site/Style Library/Provoke/main.css %>" runat="server">
The first example would always look for the style sheet in the Style Library at the root (top level) site. The second example would look for the style sheet in the current site’s Style Library. This concept can also be applied to other HTML elements such as images and ‘a’ tags as long as they include the runat=”server” attribute.
The other way of doing this is to store your resources in the wpresources folder (or any other folder) in the web application directory (located at C:\Inetpub\wwwroot\wss\VirtualDirectories\80\wpresources by default). You can then access these files from pages or web parts in your sites using
<link rel="stylesheet" type="text/css" href="/wpresources/Provoke/MediaWebPart/main.css">
This is not stored in the SharePoint content databases but can be useful if you are creating custom web parts that are shared across multiple sites or site collections and want a central place for storing resources. It can also aid development as it is easy to create a post build script to copy these files from visual studio into the correct place.
An error occurred during the processing of . The expression prefix 'SPUrl' was not recognized. Please correct the prefix or register the prefix in the <expressionBuilders> section of configuration.
even if i am using runat="server"
sandeep
26 Mar 08 at 9:26 pm
I get the same error – any solutions?
emerson
5 Oct 11 at 2:04 pm
@sandeep, @emerson – which version of SharePoint are you running? It sounds like the SPUrl expression prefix is not available (as is the case with WSS or SharePoint Foundation). An alternative way of referencing resources such as style sheets without the expression prefix is to place these in the Layouts folder (typically located at \\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS in SharePoint 2007). You can then reference these resources using a URL in the form http://siteurl/_layouts/folder/resource.css). Let me know if you need any more information.
Ari Bakker
5 Oct 11 at 11:47 pm
I suspected as much – thanks for the follow up! This was just a dev environment, the actual environment is standard, but I will keep this other solution in mind. Do you know if SP will rewrite these links (_layouts) if they are saved in a site template? It was rewriting all my root links, which was the main issue.
emerson
6 Oct 11 at 3:19 pm
Even if it does rewrite the links the beauty of the _layouts approach is that it works from all sites in all web applications. For example http://domain/_layouts/mystyles.css and http://domain/sites/sc1/_layouts/mystyles.css both reference the same file on the file system at 12\TEMPLATE\LAYOUTS\mystyles.css.
Ari Bakker
6 Oct 11 at 4:17 pm