FluentValidation

FluentValidation is an open-source library for .NET that provides a fluent, easy-to-use API for validating domain models. It allows developers to define validation rules using a fluent, chainable syntax. It separates validation rules into separate classes called validators, it supports async validation, custom validation rules, and cascading validation. It makes it easy to read and understand the validation logic, and it returns a ValidationResult object, which contains information about any validation errors that were found.