Introducing SPUrlExpressionBuilder to resolve SharePoint URL Tokens

Introduction

One of the great things when developing with SharePoint is being able to use URL tokens such as:-

• ~SiteCollection – this will resolve to the current site collection root
• ~Site – this will resolve to the current web root

For an extensive list of SharePoint URL tokens, take a look at Namwar Rizvi’s SharePoint Insight blog post, http://sharepoint-insight.com/2008/12/01/list-of-sharepoint-url-tokens/.

If you have done much with creating or modifying Master Pages or Page Layouts then these tokens become very useful to locate resources such as images, XSL or CSS files.

For example, to reference an image which is stored in a SharePoint Publishing web’s Site Collection Images folder you could use something like this:-

~SiteCollection/SiteCollectionImages/myimage.png.

Recently, I have been working with multiple language user interfaces and wanted to be able to display a different image based on the language. One of the steps to do this was to work out how to process these URL Tokens.

Solution

This is where the SPUrlExpressionBuilder class comes to the rescue. This class is part of the Microsoft.SharePoint.Publishing.WebControls assembly.

To evaluate a string with a url token like ~SiteCollectionUrl/Images/MyImage.png you can use the following SPUrlExpressionBuilder class’s method EvaluateUrlExpression().

string imagePath = SPUrlExpressionBuilder.EvaluateUrlExpression("~SiteCollection/Images/myimage.png").ToString();