Getting Started with Fluent Validation

Fluent Validation is a .NET library which provides a simple and fluent way to define validation rules in your code.

In order to get started with Fluent Validation, do the following activities

Installing FluentValidation Package

Install-Package FluentValidation

Configuration

Create Validator class and define validation rules

After installing the FluentValidation package, create validator classes that define validation rules for your models

    public class PersonValidator : AbstractValidator<Person>//validation rules for Person model/class
    {
        public PersonValidator()
        {
            RuleFor(p => p.FirstName).NotEmpty().WithMessage("First Name is required.");
            RuleFor(p => p.Age).InclusiveBetween(18, 99).WithMessage("Age must be between 18 and 99.");
            // Add more validation rules as needed
        }
    }

Configure Fluent Validation in Startup or configuration class

    services.AddValidatorsFromAssemblyContaining<PersonValidator>();

    services.AddMvc()
        .AddFluentValidation(fv => fv.RegisterValidatorsFromAssemblyContaining<PersonValidator>());

Sample Usage

After installing and configuring FluentValidation, this is a sample use case to see how it works.

Class with properties to validate

    public class Person
    {
        public string FirstName { get; set; }
        public int Age { get; set; }
    }

Inject Validator interface into Controllers and Validate data

    public class PersonController : Controller
    {
        private readonly IValidator<Person> _personValidator;

        public PersonController(IValidator<Person> personValidator)
        {
            _personValidator = personValidator;
        }

        [HttpPost]
        public IActionResult CreatePerson(Person person)
        {
            var validationResult = _personValidator.Validate(person);
            if (!validationResult.IsValid)
            {
                return BadRequest(validationResult.Errors);
            }

            return Ok();
        }
    }

Further Readings

Follow this link to learn more.

Was this page helpful?

Happy React is loading...