Normalizing user-provided values

In this tutorial, we'll see how to normalize (clean-up) input when creating value objects.

We'll create a type that represents a vehicle registration plate in the UK. Vehicle registration plates vary from country to country, but in the UK, they are all upper case, e.g. AB12 XYZ.

Create a VehicleRegistrationPlate type:

[ValueObject<string>] 
public partial struct VehicleRegistrationPlate 
{
}

By default, creating one and using it does nothing with the value provided:

var plate = VehicleRegistrationPlate.From("ab12 xyz");
Console.WriteLine(plate);

>> ab12 xyz

Now, add the following method:

private static string NormalizeInput(string input) => 
    input.ToUpperInvariant();

... and run it again to see that the data has been normalized as upper-case.

var plate = VehicleRegistrationPlate.From("ab12 xyz");
Console.WriteLine(plate);

>> AB12 XYZ

Note that normalization happens before validation, so your method might get passed invalid raw data.

Also note that if you validate your values, then validation happens on the sanitized value.

Last modified: 16 September 2024