FluentValidation Rule Sets

#testing #csharp #dotnetcore

Introduction

Learn how to use rule sets which allow developers to group validation rules together which can be executed together as a group whilst ignoring other rules or execute all rules.

The conventional use of Fluent Validation is to create a model followed by creating a validator class. In the example below, each property has there own validator class which allows reuse.

public class PersonValidator : AbstractValidator<IPerson>
{
    public PersonValidator()
    {
        Include(new IdentifierValidator());
        Include(new FirstNameValidator());
        Include(new LastNameValidator());
        Include(new BirthDateValidator());
        Include(new AddressValidator());
        Include(new EmailValidator());
    }
}

Sample property validator for FirstName property.

public class FirstNameValidator : AbstractValidator<IPerson>
{
    public FirstNameValidator()
    {
        RuleFor(person => person.FirstName)
            .NotEmpty()
            .MinimumLength(3);
    }
}

Using conventional validation works great the majority of work for validation. There are times when not all properties require validations like when adding a new record for EF Core which assigns an identifier.

Rule sets

Rules sets are setup as shown below where FirstName and LastName are a group while other properties are setup separately. This means that rules can be included or excluded for validating an object.

public class PersonValidator : AbstractValidator<Person>
{

    public PersonValidator()
    {
        RuleSet("Names", () =>
        {
            RuleFor(x => x.FirstName).NotNull();
            RuleFor(x => x.LastName).NotNull();
        });

        RuleSet("Identifier", () =>
        {
            RuleFor(x => x.PersonId).NotEqual(0);
        });

        RuleSet("Birth", () =>
        {
            RuleFor(x => x.BirthDate).BirthDateRule();
        });

        RuleSet("Email", () =>
        {
            RuleFor(x => x.EmailAddress).NotEmpty().EmailAddress();
        });
    }
}

Example to exclude the Identifier rule.

var validator = new PersonValidator();

ValidationResult result = validator.Validate(MockedData.InvalidPerson, options => options.IncludeRuleSets(
    "Names",
    "Birth"));


if (result.IsValid)
{
    Console.WriteLine("Validation succeeded.");
}
else
{
    foreach (var error in result.Errors)
    {
        AnsiConsole.MarkupLine($"{error.PropertyName,-14} [red]Error:[/] {error.ErrorMessage}");
    }
}

Example to include all rules

Using the wildcard indicates to include all rules.

var validator = new PersonValidator();

// Use wildcard to include all rule sets

var result = validator.Validate(
    MockedData.InvalidPerson, options => options.IncludeRuleSets("*"));

if (result.IsValid)
{
    Console.WriteLine("Validation succeeded.");
}
else
{
    foreach (var error in result.Errors)
    {
        AnsiConsole.MarkupLine($"{error.PropertyName,-14} [red]Error:[/] {error.ErrorMessage}");
    }
}