Round #855

Write a FluentValidation AbstractValidator<T> for a 'RegisterUser' command: email (valid format), password (≥ 8 chars, has digit and symbol), age (18+).

### RegisterUserValidator ```csharp using FluentValidation; public class RegisterUser { public string Email { get; set; } public string Password { get; set; } public int Age { get; set; } } public class RegisterUserValidator : AbstractValidator<RegisterUser> { public RegisterUserValidator() { RuleFor(x => x.Email) .NotEmpty() .WithMessage("Email is required") .EmailAddress() .WithMessage("Invalid email format"); RuleFor(x => x.Password) .NotEmpty() .WithMessage("Password is required") .MinimumLength(8) .WithMessage("Password must be at least 8 characters") .Matches(@"^(?=.*\d)(?=.*[^a-zA-Z0-9]).*$") .WithMessage("Password must contain at least one digit and one symbol"); RuleFor(x => x.Age) .GreaterThanOrEqualTo(18) .WithMessage("Age must be 18 or older"); } } ``` ### Example Usage ```csharp public class Program { public static void Main() { var validator = new RegisterUserValidator(); var registerUser = new RegisterUser { Email = "test@example.com", Password = "P@ssw0rd", Age = 25 }; var results = validator.Validate(registerUser); if (!results.IsValid) { foreach (var failure in results.Errors) { Console.WriteLine($"Property {failure.PropertyName} failed validation. Error: {failure.ErrorMessage}"); } } else { Console.WriteLine("Validation successful"); } } } ``` This code defines a `RegisterUserValidator` class that inherits from `AbstractValidator<RegisterUser>`. It uses FluentValidation's `RuleFor` method to define validation rules for the `Email`, `Password`, and `Age` properties of the `RegisterUser` class. The `Email` property is validated to ensure it is not empty and has a valid email format. The `Password` property is validated to ensure it is not empty, has a minimum length of 8 characters, and contains at least one digit and one symbol. The `Age` property is validated to ensure it is greater than or equal to 18. In the example usage, a `RegisterUser` object is created and validated using the `RegisterUserValidator`. If the validation fails, the error messages are printed to the console. If the validation succeeds, a success message is printed.

```csharp using FluentValidation; public class RegisterUserCommand { public string Email { get; set; } public string Password { get; set; } public int Age { get; set; } } public class RegisterUserCommandValidator : AbstractValidator<RegisterUserCommand> { public RegisterUserCommandValidator() { RuleFor(x => x.Email) .NotEmpty() .EmailAddress() .WithMessage("Invalid email format"); RuleFor(x => x.Password) .NotEmpty() .MinimumLength(8) .Matches(@"[0-9]") .WithMessage("Password must contain at least one digit") .Matches(@"[!@#$%^&*()_+=\[{};:'<>,./?]") .WithMessage("Password must contain at least one symbol"); RuleFor(x => x.Age) .GreaterThanOrEqualTo(18) .WithMessage("Age must be 18 or older"); } } ``` This implementation uses FluentValidation's `AbstractValidator<T>` to define validation rules for the `RegisterUserCommand` class. The `RuleFor` method is used to specify validation rules for each property, and the `WithMessage` method is used to provide a custom error message for each rule. The `Matches` method is used with regular expressions to validate the password format. To use this validator, you would create an instance of it and call the `Validate` method, passing in an instance of `RegisterUserCommand`. The `Validate` method returns a `ValidationResult` object, which contains a list of validation errors if any rules are not met. Note that this implementation does not include any dependency injection or error handling beyond what is provided by FluentValidation. Depending on your application's requirements, you may need to add additional error handling or registration code. This implementation requires more text to fully explain the usage and integration with the application.