C# add validation on a setter method

Question

I have a a couple of variables that i define in C# by:

public String firstName { get; set; }
public String lastName { get; set; }
public String organization          


        

Answer 1

It's best practice to apply SRP. Set the validation in a separate class.

You can use FluentValidation

       Install-Package FluentValidation

You would define a set of validation rules for Customer class by inheriting from AbstractValidator:

Example:

  public class CustomerValidator : AbstractValidator {
    public CustomerValidator() {
      RuleFor(x => x.Surname).NotEmpty();
      RuleFor(x => x.Forename).NotEmpty().WithMessage("Please specify a first name");
      RuleFor(x => x.Discount).NotEqual(0).When(x => x.HasDiscount);
      RuleFor(x => x.Address).Length(20, 250);
      RuleFor(x => x.Postcode).Must(BeAValidPostcode).WithMessage("Please specify a valid postcode");
    }

    private bool BeAValidPostcode(string postcode) {
      // custom postcode validating logic goes here
    }
  }

To run the validator, instantiate the validator object and call the Validate method, passing in the object to validate.

   Customer customer = new Customer();
   CustomerValidator validator = new CustomerValidator();

   ValidationResult result = validator.Validate(customer);

 if(! results.IsValid) {
   foreach(var failure in results.Errors) {
       Console.WriteLine("Property " + failure.PropertyName + " failed validation. Error was: " + failure.ErrorMessage);

} }