fluentvalidation-patterns

FluentValidation Patterns

FluentValidation patterns for ABP Framework input DTO validation.

When to Use

• Creating validators for Create/Update DTOs
• Implementing async validation with repository checks
• Building conditional validation rules
• Creating reusable custom validators
• Localizing validation error messages

ABP Integration

Basic Validator Structure

// Application/{Feature}/CreateUpdate{Entity}DtoValidator.cs
public class CreateUpdate{Entity}DtoValidator : AbstractValidator<CreateUpdate{Entity}Dto>
{
    public CreateUpdatePatientDtoValidator()
    {
        RuleFor(x => x.FirstName)
            .NotEmpty()
            .MaximumLength(100);

        RuleFor(x => x.LastName)
            .NotEmpty()
            .MaximumLength(100);

        RuleFor(x => x.Email)
            .NotEmpty()
            .EmailAddress()
            .MaximumLength(255);

        RuleFor(x => x.DateOfBirth)
            .NotEmpty()
            .LessThan(DateTime.Today)
            .WithMessage("Date of birth must be in the past");
    }
}

ABP Module Registration

// ApplicationModule.cs
public override void PreConfigureServices(ServiceConfigurationContext context)
{
    PreConfigure<AbpFluentValidationAutoValidationOptions>(options =>
    {
        options.AutoValidateMethodInvocations = true;
    });
}

public override void ConfigureServices(ServiceConfigurationContext context)
{
    // Auto-register all validators in assembly
    context.Services.AddValidatorsFromAssembly(typeof({ProjectName}ApplicationModule).Assembly);
}

Common Validation Rules

String Validation

RuleFor(x => x.Name)
    .NotEmpty()
    .WithMessage("Name is required")
    .MinimumLength(2)
    .MaximumLength(100)
    .Matches(@"^[a-zA-Z\s]+$")
    .WithMessage("Name can only contain letters and spaces");

RuleFor(x => x.Email)
    .NotEmpty()
    .EmailAddress()
    .Must(email => !email.EndsWith("@test.com"))
    .WithMessage("Test emails are not allowed");

RuleFor(x => x.Phone)
    .NotEmpty()
    .Matches(@"^\+?[1-9]\d{1,14}$")
    .WithMessage("Invalid phone number format");