1 using FluentValidation;
 2 public class CustomerValidator: AbstractValidator<Customer> {
 3   public CustomerValidator() {
 4     RuleFor(customer => customer.Surname).NotEmpty();
 5     RuleFor(customer => customer.Forename).NotEmpty().WithMessage("Please specify a first name");
 6     RuleFor(customer => customer.Company).NotNull();
 7     RuleFor(customer => customer.Discount).NotEqual(0).When(customer => customer.HasDiscount);
 8     RuleFor(customer => customer.Address).Length(20, 250);
 9     RuleFor(customer => customer.Postcode).Must(BeAValidPostcode).WithMessage("Please specify a valid postcode");
10   }
11   private bool BeAValidPostcode(string postcode) {
12     // custom postcode validating logic goes here
13   }
14 }
15 Customer customer = new Customer();
16 CustomerValidator validator = new CustomerValidator();
17 ValidationResult results = validator.Validate(customer);
18 bool validationSucceeded = results.IsValid;
19 IList<ValidationFailure> failures = results.Errors;