lozanotek/mvcturbine — pull request #19 by jaredmcguire (2012-03-12 21:38:10+00:00)
Title: Virtual path provider chaining

When you register a virtual path provider, it is added to a chain of providers. We should use the Previous property to hand processing off to the previous provider in the chain if the requested path is not handled by our provider. The chain always ends with the default ASP.NET provider, which serves files from the file system.

http://msdn.microsoft.com/en-us/library/system.web.hosting.virtualpathprovider.previous.aspx