restworld-validation

Add custom validation to a RESTworld CRUD endpoint. Use when asked to validate DTOs before or after create/update, reject a request with a 400 validation error, add business-rule checks (uniqueness, limits, immutable fields, cross-field rules), write a validator class, derive from ValidatorBase, CreateValidatorBase or UpdateValidatorBase, return ValidationResults / IValidationResults, register a validator with AddValidator, AddCreateValidator or AddUpdateValidator, understand AddValidationAndErrorHandling, ValidationService or the problem details / errors dictionary returned to the client, or validate collections (ValidateCollectionBeforeCreateAsync etc.).