NRules 

Canonical rules model to define rules for the NRules rules engine.

Execution engine for the NRules rules engine.

Fluent DSL for authoring rules in C# with the NRules rules engine.

NRules is an open source rules engine for .NET that is based on the Rete matching algorithm with rules authored in C# using internal DSL.

Autofac integration for NRules

Business rules language for NRules rules engine.

JSON serialization for the NRules rules engine.

Rules unit testing harness for NRules.

.NET dependency injection integration for NRules

SimpleInjector integration for NRules