Fluent Validation for .NET

using FluentValidation;
 
public class CustomerValidator: AbstractValidator<Customer> {
  public CustomerValidator() {
    RuleFor(customer => customer.Surname).NotEmpty();
    RuleFor(customer => customer.Forename).NotEmpty().WithMessage("Please specify a first name");
    RuleFor(customer => customer.Company).NotNull();
    RuleFor(customer => customer.Discount).NotEqual(0).When(customer => customer.HasDiscount);
    RuleFor(customer => customer.Address).Length(20, 250);
    RuleFor(customer => customer.Postcode).Must(BeAValidPostcode).WithMessage("Please specify a valid postcode");
  }
 
  private bool BeAValidPostcode(string postcode) {
    // custom postcode validating logic goes here
  }
}
 
Customer customer = new Customer();
CustomerValidator validator = new CustomerValidator();
ValidationResult results = validator.Validate(customer);
 
bool validationSucceeded = results.IsValid;
IList<ValidationFailure> failures = results.Errors;

• Creating a Validator Class
• Built in Validators
• NotNull Validator
• NotEmpty Validator
• NotEqual Validator
• Length Validator
• Less Than Validator
• Less Than Or Equal Validator
• Greater Than Validator
• GreaterThan Or Equal Validator
• Predicate Validator
• Configuring/Customising a validator
• Overriding the default error message
• Overriding the default property name
• Specifying a condition with When/Unless
• Custom Validators
• Writing a custom Property Validator
• Using AbstractValidator.Custom
• Testing Validators
• Integrating with ASP.NET MVC