Form validation

DataAnnotations attributes for the HeroKit validators. They work with ASP.NET Core model validation, Blazor's DataAnnotationsValidator, minimal API filters and Validator.TryValidateObject.

using System.ComponentModel.DataAnnotations;
using HeroKit.Validation;

public sealed class Customer
{
    [Required, Tckn]
    public string? IdentityNumber { get; set; }

    [TaxId("TR")]
    public string? TaxId { get; set; }

    [Iban]
    public string? Iban { get; set; }

    [PhoneNumber("TR", MobileOnly = true, ErrorMessage = "Cep telefonu geçersiz.")]
    public string? Mobile { get; set; }

    [PostalCode("TR")]
    public string? PostalCode { get; set; }

    [VehiclePlate("TR")]
    public string? Plate { get; set; }

    [CardNumber]
    public string? Card { get; set; }

    [GibInvoiceNumber]
    public string? InvoiceNumber { get; set; }

    [Ettn]
    public string? Ettn { get; set; }
}

Attribute	Checks
`[Tckn]`	Turkish identity number checksum
`[Vkn]`	Turkish tax number checksum
`[Iban]`	ISO 13616 mod-97; national length where a country has IBAN rules (TR: 26)
`[CardNumber]`	Length and Luhn
`[GibInvoiceNumber]`	e-Fatura / e-Arşiv invoice number in the GİB format, for example `ABC2026000000001`
`[Ettn]`	ETTN: a non-empty UUID in the 8-4-4-4-12 format
`[KepAddress]`	KEP address: an e-mail address on a `.kep.tr` domain
`[IdCardSerial]`	Chip identity card serial number, for example `A12B34567`
`[Mersis]`	MERSİS number: "0", a valid VKN and a 5-digit serial
`[Gtin]`	Barcode number (EAN-8, UPC-A, EAN-13, GTIN-14) with the GS1 check digit
`[PhoneNumber("TR")]`	Phone number of a country; `MobileOnly = true` for mobiles
`[VehiclePlate("TR")]`	Vehicle plate of a country
`[PostalCode("TR")]`	Postal code of a country (TR: 5 digits, valid province prefix)
`[NationalId("TR")]`	National identity number of a country (TR: TCKN)
`[TaxId("TR")]`	Tax identifier of a country (TR: VKN or TCKN)

The country attributes take an ISO 3166-1 alpha-2 code. The country is looked up in Countries when a value is validated, so a country you add with Countries.Register works too. See Countries and languages. A country without the needed rules throws NotSupportedException.

FluentValidation

The separate HeroKit.FluentValidation package adds the same checks as FluentValidation rules. The core package stays dependency-free.

dotnet add package HeroKit.FluentValidation

using FluentValidation;
using HeroKit.FluentValidation;
using HeroKit.Globalization;

public sealed class CustomerValidator : AbstractValidator<Customer>
{
    public CustomerValidator()
    {
        RuleFor(x => x.IdentityNumber).NotEmpty().Tckn();
        RuleFor(x => x.Iban).Iban();
        RuleFor(x => x.Mobile).PhoneNumber(Countries.Turkey, mobileOnly: true);
        RuleFor(x => x.Plate).VehiclePlate(Countries.Turkey);
        RuleFor(x => x.InvoiceNumber).GibInvoiceNumber();
    }
}

Rules: Tckn, Vkn, Iban, CardNumber, GibInvoiceNumber, Ettn, Mersis, Gtin, KepAddress, IdCardSerial, and the country rules PhoneNumber(country, mobileOnly), VehiclePlate(country), PostalCode(country), NationalId(country), TaxId(country). Messages use {PropertyName}; replace them with WithMessage.

Notes

Null and empty values are valid, so optional fields stay optional. Add [Required] to require a value. Default messages are English and include the field name; set ErrorMessage or resource properties to localize them.

Table of Contents

Form validation

FluentValidation

Notes