Windows Workflow Foundation (WF) which is shipped as part of .Net Framework 3.0 provides rules engine capabilities that allows you to seamlessly integrate rules support into your workflows. It can also be leveraged outside of workflows to provide rules functionality to any .Net application. The Windows Workflow Foundation Rules Team just published a sample on the WF Community Website that shows how to use WF Rules outside the context of the workflow to control and drive the page flow of an ASP.Net application. Check the sample out here.
To learn more about WF Rules Engine, check the Introduction to the Windows Workflow Foundation Rules Engine MSDN Article here, the Windows SDK here for samples and technology documentation, the WF section in the online MSDN library, and the community website for more WF samples and more Rules samples.
Thanks, --Moustafa