README.md

Validation Samples

The purpose of this project is to demonstrate various techniques and methods for using FluentValidation to validate business objects.

This is an examples-based Visual Studio solution where each type of example is surfaced through an associated folder. Each folder has an associated readme.md that provides additional technical information about the example.

Solution
  - readme.md
  /example-1
    - readme.md
    - example web page 
  /example-2
    - readme.md
    - example web page 

The example scenarios are:

• Using data annotations and model state
• Create a fluent-validator to validate a business object
• Invoke a fluent-validator manually and map validation errors to model state
• Implement validation is as a cross-cutting concern using decoration
• Implement validation is as a cross-cutting concern using MediatR pipeline behaviours
• Introduce ExceptionFilters for handling validation errors as a cross-cutting concern
• Validating a collection
• Validating a business object based on data stored in a database
• Introduce unit tests to test validation logic for business rules

You can see an examples of a simple validator in the Samples.Core.Models folder. The following code snippet shows a simple validator for the Person object

using FluentValidation;

namespace Samples.Core.Models
{
    public record Person(string? Name, int? Age);

    public class PersonValidator : AbstractValidator<Person>
    {
        public PersonValidator()
        {
            RuleFor(x => x.Name).NotEmpty();
            RuleFor(x => x.Age).NotEmpty()
                .InclusiveBetween(5, 65)
                .WithMessage("The person's age must be between 5 and 65.");
        }
    }
}