TurkishId

Validator, model binder and generator tool for Turkish Republic's citizen ID numbers. I've decided to give this a shot last night while I was waiting for a download. And Turkish ID numbers were really popular in Turkish social media last week. The Id number is called "T.C. Kimlik No" (Turkish Republic Identity Number). I decided to use English translation to allow easier handling in international projects.

Usage

I wanted the TurkishIdNumber representation to be used anywhere in the code as a value to pass around when using id's allowing to assume an instance is already validated saving you from redundant checks.

When you want to use it as a representation of an ID number:

using TurkishId;
var id = new TurkishIdNumber("12345678901");
// throws ArgumentException when invalid parameter is passed

or if you just want to validate it:

using TurkishId;
bool reallyValid = TurkishIdNumber.IsValid("12345678901");

You can also use the classic TryParse:

using TurkishId;
if (TurkishIdNumber.TryParse(value, out var id))
{
    // ...
}

or with a nullable return value which can be used with pattern matching:

using TurkishId;
if (TurkishIdNumber.TryParse(value) is TurkishIdNumber id))
{
    // ...
}

NuGet package is here: https://www.nuget.org/packages/TurkishId/

TurkishId.ModelBinder

There is also a model binder package that you can install at https://www.nuget.org/packages/TurkishId.ModelBinder. It's a plug'n'play model binder which lets you to use TurkishIdNumber class directly in your model declarations.

It's not part of the original package because you may not want to have whole MVC as a dependency.

To set it up in an ASP.NET Core project, use this syntax in your ConfigureServices() method in your Startup class:

services.AddMvc(options =>
{
  options.ModelBinderProviders.Insert(0, new TurkishIdModelBinderProvider());
});

and you're done. If you'd like to use it in your Razor Pages app use AddMvcOptions instead:

services.AddRazorPages()
  .AddMvcOptions(options => options.ModelBinderProviders.Insert(0, new TurkishIdModelBinderProvider()));

or, alternatively, if you only use controllers, you can add it to your AddControllers options:

services.AddControllers(options =>
{
  options.ModelBinderProviders.Insert(0, new TurkishIdModelBinderProvider());
});

The model binder package will use ASP.NET Core's model binding message providers. You can now localize them like how you do any other model binder.

Performance

This is probably one of the fastest implementations on .NET. I didn't grind so much on performance but it can easily handle millions of validations per second on my Core i7.

Algorithm

Turkish Republic's ID structure and verification is simple. It's an eleven digit number. If we name each digit as d(n) where leftmost digit is called d1 and the rightmost d11, a given ID is valid if:

d1 > 0

and

n = (d1 + d3 + d5 + d7 + d9) * 7 - (d2 + d4 + d6 + d8)

if n < 0 then n = n + 10

d10 = n mod 10

and

d11 = sum(d1..d10) mod 10