TNG / ArchUnitNET

A C# architecture test library to specify and assert architecture rules in C# for automated testing.

microsoft / RulesEngine

A fast and reliable .NET Rules Engine with extensive Dynamic expression support

FluentValidation / FluentValidation

A popular .NET validation library for building strongly-typed validation rules.

NRules / NRules

Rules engine for .NET, based on the Rete matching algorithm, with internal DSL in C#.

lithnet / ad-password-protection

Active Directory password filter featuring breached password checking and custom complexity rules

DotNetAnalyzers / StyleCopAnalyzers

An implementation of StyleCop rules using the .NET Compiler Platform

microsoft / DevSkim

DevSkim is a set of IDE plugins, language analyzers, and rules that provide security "linting" capabilities.