CheckDigits.Net.FluentValidation 1.0.0

CheckDigits.Net.FluentValidation

CheckDigits.Net.FluentValidation integrates the CheckDigits.Net library with FluentValidation, providing validators for check digit algorithms in .NET applications.

For full documentation of the various check digit algorithms supported, please refer to the CheckDigits.Net README file.

Using CheckDigits.Net.FluentValidation

Install the CheckDigits.Net.FluentValidation package via command line:

dotnet add package CheckDigits.Net.FluentValidation --version 1.0.0

or by searching for "CheckDigits.Net.FluentValidation" in your IDE's Package Manager.

Once installed, you can use the CheckDigit(ICheckDigitAlgorithm) extension method to include check digit validation in your FluentValidation validators. You can use any of the algorithms provided in the CheckDigits.Net package or your own custom implementations. The supplied algorithm must be stateless and thread-safe.

For example, to validate that a UPC code conforms to the Modulus10_13 algorithm included in CheckDigits.Net (the algorithm used by EAC, GTIN, ISBN-13, UPC and other international standard identifiers), you would do the following:

using CheckDigits.Net.GeneralAlgorithms;
using CheckDigits.Net.FluentValidation;

public class ProductDetails
{
	public string UpcCode { get; set; }
	
	// Other properties...
}

public class ProductDetailsValidator : AbstractValidator<ProductDetails>
{
	public ProductDetailsValidator()
	{
		RuleFor(x => x.UpcCode)
			.NotEmpty()
			.CheckDigit(Algorithms.Modulus10_13);		// Using a predefined, lazy created instance of the Modulus10_13 algorithm
	}
}

By default, the error message for an invalid check digit will be: {PropertyName} must have valid {AlgorithmName} check digit(s). You may use the FluentValidation mechanisms to customize the error message as needed.

Note the use of the NotEmpty() method to ensure that the property is not null, empty or whitespace. The check digit validator does not perform null, empty or whitespace checks by default and should be used in conjunction with NotEmpty() when necessary.

In cases where you need to use a custom implementation of ICheckDigitAlgorithm, you can do so by creating an instance of your algorithm and passing it to the CheckDigit method:

public class ProductDetailsValidator : AbstractValidator<ProductDetails>
{
	public ProductDetailsValidator()
	{
		RuleFor(x => x.UpcCode)
			.NotEmpty()
			.CheckDigit(new Modulus10_13Algorithm());		// Instantiate the Modulus10_13 algorithm directly
	}
}

A common use case for custom implementations is when you need to use the Iso7064HybridSystemAlgorithm, Iso7064PureSystemDoubleCharacterAlgorithm or Iso7064PureSystemSingleCharacterAlgorithm classes to validate check digits that use custom character sets.

Masked Check Digit Algorithms

There are cases where values being validated may include formatting characters that should be ignored when performing check digit validation (for example, a credit card number that has been formatted with spaces, '1234 5678 9012 3456'). CheckDigits.Net supports this scenario through the use of check digit masks. An algorithm that supports check digit masks implements the IMaskedCheckDigitAlgorithm interface which extends ICheckDigitAlgorithm to indicate that it can work with masks (currently, only the Luhn algorithm does so, but additional algorithms will be added in the future).

To use a check digit mask, create a class that implements the ICheckDigitMask interface (defined in the CheckDigits.Net namespace). The check digit mask class must be stateless and thread-safe.

Then, use the MaskedCheckDigit(IMaskedCheckDigitAlgorithm, ICheckDigitMask) extension method to add the masked check digit validator to the property rules. For example:

// Excludes every 5th character, allowing for spaces or dashes in credit card numbers.
public class CreditCardMask : ICheckDigitMask
{
   public Boolean ExcludeCharacter(Int32 index) => (index + 1) % 5 == 0;

   public Boolean IncludeCharacter(Int32 index) => (index + 1) % 5 != 0;
}

public class PaymentDetails
{
	public string CardNumber { get; set; }
	
	// Other properties...
}

public class PaymentDetailsValidator : AbstractValidator<PaymentDetails>
{
	public PaymentDetailsValidator()
	{
		RuleFor(x => x.CardNumber)
			.NotEmpty()
			.MaskedCheckDigit(new LuhnAlgorithm(), new CreditCardMask());
	}
}

Release History/Release Notes

v1.0.0

Initial release. Supports CheckDigit and MaskedCheckDigit validators for FluentValidation.