Rather than build a new rules engine, why not just use a product or a nuget package that’s already out there?

Some Business Rule Engine products and package on the market.

Project Open Source Nuget Package Integrated Testing Coding Required Most Recent Update Most Recent YouTube Video
Vergosity .NET Business Logic & Rules Framework Yes Yes No Yes 2013 2014
Yet Another Rules Engine for .NET Yes Yes No Yes 2013 Never
InRule No No Yes No Current Current
Drool.Net Yes No No No 2007 2013
NxBRE Yes No No Yes 2012 Never
BizTalk No No Yes No Current Current
Windows Workflow Foundation No Yes No No Current Current
Micro Rule Engine Yes No No Yes 2012 Never

From where I’m sitting. NxBRE seems to be the most active, flexible, open and comprehensive solution.