LuhnDotNet

A C# implementation of the Luhn algorithm and other check digit algorithms, which can be used to validate identification numbers like credit card numbers, International Securities Identification Numbers (ISINs), ISBN, PZN and more.

The Luhn algorithm is a checksum formula used to validate identification numbers like credit card numbers. It works by doubling every second digit from the right, summing all the digits, and checking if the total is a multiple of 10. It's widely used and is specified in ISO/IEC 7812-1.

The Modulo 11 algorithm with ascending weights is another checksum formula used to validate identification numbers like PZN (Pharmazentralnummer) and ISBN-10. It works by multiplying each digit by a weight, summing the results, and calculating the check digit based on the modulo 11 of the sum.

Build & Test Status Of Default Branch

Solution	Project Format	.NET Version
`LuhnDotNet.sln`	SDK	Standard 2.0
		Standard 2.1
		FX 4.6.2
		FX 4.7
		FX 4.7.1
		FX 4.7.2
		FX 4.8
		.NET 8
		.NET 9

NuGet

Supported Target Frameworks

Build And Test Status	NuGet Version	Git Tag	Target Frameworks
			.NET 8
			.NET 9
			Standard 2.0
			Standard 2.1
			FX 4.6.2
			FX 4.7
			FX 4.7.1
			FX 4.7.2
			FX 4.8

Install LuhnDotNet package

Open a console and switch to the directory, containing your project file.
Use the following command to install version 2.0.1 of the LuhnDotNet package:
```
dotnet add package LuhnDotNet -v 2.0.1 -f <FRAMEWORK>
```
After the completion of the command, look at the project file to make sure that the package is successfully installed.

You can open the .csproj file to see the added package reference:
```
<ItemGroup>
  <PackageReference Include="LuhnDotNet" Version="2.0.1" />
</ItemGroup>
```

Remove LuhnDotNet package

Open a console and switch to the directory, containing your project file.
Use the following command to remove the LuhnDotNet package:
```
dotnet remove package LuhnDotNet
```
After the completion of the command, look at the project file to make sure that the package is successfuly removed.

You can open the .csproj file to check the deleted package reference.

API Documentation

You can find the API documentation here.

Usage

Identification Number	Check Digit Algorithm
Credit Card Number	Luhn
International Securities Identification Number (ISIN)	Luhn
Deutsche Bahn AG (DB) locomotive number	Luhn
UIC identification marking for tractive stock	Luhn
New Format for Singapore IP Application Numbers at IPOS	Damm
German Pharmazentralnummer (PZN)	Modulo 11 with ascending weights
Austrian Pharmazentralnummer (PZN)	Modulo 11 with ascending weights
ISBN-10	Modulo 11 with ascending weights

Luhn Algorithm

Compute the Luhn check digit

using System;
using System.Collections.Generic;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example1
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var checkDigit = "37828224631000".ComputeLuhnCheckDigit();
            //// Must be 5
            Console.WriteLine(checkDigit);
        }
    }
}

Compute the Luhn number

using System;
using System.Collections.Generic;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example2
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var luhnNumber = "37828224631000".ComputeLuhnNumber();
            //// Must be 378282246310005
            Console.WriteLine(luhnNumber);
        }
    }
}

Validate Luhn number

using System;
using System.Collections.Generic;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example3
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var isValid = "378282246310005".IsValidLuhnNumber();
            //// Must be 'true'
            Console.WriteLine(isValid);
        }
    }
}

Validate number and corresponding Luhn check digit

using System;
using System.Collections.Generic;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example4
{
    public class Program
    {
        public static void Main(string[] args)
        {
            char checkDigit = '5';
            var isValid = checkDigit.IsValidLuhnCheckDigit("37828224631000");
            //// Must be 'true'
            Console.WriteLine(isValid);
        }
    }
}

Validate ISIN with LuhnDotNet and AlphaNumericToNumeric

The LuhnDotNet library can be used in combination with the AlphaNumericToNumeric method to validate an International Securities Identification Number (ISIN). An ISIN uniquely identifies a security, such as stocks, bonds or derivatives. It is a 12-character alphanumeric code.

The AlphaNumericToNumeric method is used to convert the alphanumeric ISIN to a numeric string, where each letter in the input string is replaced by its decimal ASCII value minus 55. This numeric string can then be validated using the Luhn.IsValid method.

Here is an example of how to use these methods to validate an ISIN:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example5
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string isin = "US0378331005";
            bool isValid = isin.AlphaNumericToNumeric().IsValidLuhnNumber();
            Console.WriteLine($"The ISIN {isin} is valid: {isValid}");
        }
    }
}

Compute ISIN Check Digit with LuhnDotNet and AlphaNumericToNumeric

The LuhnDotNet library provides the ComputeLuhnCheckDigit method which can be used to compute the check digit of a numeric string according to the Luhn algorithm. When dealing with an International Securities Identification Number (ISIN), which is a 12-character alphanumeric code, we first need to convert the alphanumeric ISIN to a numeric string. This can be achieved using the AlphaNumericToNumeric method.

Here is an example of how to compute the check digit of an ISIN:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example6
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string isinWithoutCheckDigit = "US037833100";
            char checkDigit = isinWithoutCheckDigit.AlphaNumericToNumeric().ComputeLuhnCheckDigit();
            Console.WriteLine($"The check digit for ISIN {isinWithoutCheckDigit} is: {checkDigit}");
        }
    }
}

Compute credit card number with LuhnDotNet

The LuhnDotNet library can be used to compute the check digit of a credit card number. The check digit is the last digit of the credit card number, which is used to validate the number according to the Luhn algorithm.

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example7
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string creditCardNumberWithoutCheckDigit = "4417 1234 5678 911".RemoveSeparators();
            char checkDigit = creditCardNumberWithoutCheckDigit.ComputeLuhnCheckDigit();
            Console.WriteLine($"The check digit for credit card number {creditCardNumberWithoutCheckDigit} is: {checkDigit}");
        }
    }
}

Validate credit card number with LuhnDotNet

The LuhnDotNet library can be used to validate a credit card number according to the Luhn algorithm. The IsValid method returns true if the credit card number is valid, and false otherwise.

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Luhn;

namespace Example8
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string creditCardNumber = "4417 1234 5678 9113".RemoveSeparators();
            bool isValid = creditCardNumber.IsValidLuhnNumber();
            Console.WriteLine($"The credit card number {creditCardNumber} is valid: {isValid}");
        }
    }
}

Modulo 11 Algorithm with ascending weights

This implementation uses sum modulo 11 as a direct remainder and can't be used for ISSN.

Compute the Modulo 11 check digit

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example9
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var checkDigit = "809027341".ComputeMod11CheckDigit();
            //// Must be 6
            Console.WriteLine(checkDigit);
        }
    }
}

Compute the Modulo 11 number

using System;
using System.Collections.Generic;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example10
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var mod11Number = "809027341".ComputeMod11Number();
            //// Must be 8090273416
            Console.WriteLine(mod11Number);
        }
    }
}

Validate Modulo 11 number

using System;
using System.Collections.Generic;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example11
{
    public class Program
    {
        public static void Main(string[] args)
        {
            var isValid = "8090273416".IsValidMod11Number();
            //// Must be 'true'
            Console.WriteLine(isValid);
        }
    }
}

Validate number and corresponding Modulo 11 check digit

using System;
using System.Collections.Generic;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example12
{
    public class Program
    {
        public static void Main(string[] args)
        {
            char checkDigit = '6';
            var isValid = checkDigit.IsValidMod11CheckDigit("809027341");
            //// Must be 'true'
            Console.WriteLine(isValid);
        }
    }
}

Validate PZN with Modulo 11

The LuhnDotNet library can also be used to validate a Pharmazentralnummer (PZN), which is a unique identifier for pharmaceuticals in Germany. The PZN is a 8-digit number, and the last digit is a check digit calculated using the Modulo 11 algorithm. Here is an example of how to validate a PZN using the LuhnDotNet library:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example13
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string pzn = "06789572";
            bool isValid = pzn.IsValidMod11Number();
            Console.WriteLine($"The German PZN {pzn} is valid: {isValid}");
        }
    }
}

The LuhnDotNet library can also be used to validate an Austrian Pharmazentralnummer (PZN), which is a unique identifier for pharmaceuticals in Austria. The PZN is a 7-digit number, with the last digit being a check digit calculated using the Modulo 11 algorithm. Add a leading zero to the PZN to make it an 8-digit number, as the Mod11 algorithm expects an 8-digit input. The last digit is the check digit, which is calculated using the Modulo 11 algorithm. Here is an example of how to validate an Austrian PZN using the LuhnDotNet library:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;
    
namespace Example14
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string pzn = "0" + "3855587";
            bool isValid = pzn.IsValidMod11Number();
            Console.WriteLine($"The Austrian PZN {pzn} is valid: {isValid}");
        }
    }
}

Compute PZN Check Digit with Modulo 11

The LuhnDotNet library can be used to compute the check digit of a Pharmazentralnummer (PZN) using the Modulo 11 algorithm. The PZN is a unique identifier for pharmaceuticals in Germany and Austria, and the last digit is a check digit calculated using the Modulo 11 algorithm. Here is an example of how to compute the check digit of a PZN using the LuhnDotNet library:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example15
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string pznWithoutCheckDigit = "0678957";
            char checkDigit = pznWithoutCheckDigit.ComputeMod11CheckDigit();
            //// Must be 2
            Console.WriteLine($"The check digit for PZN {pznWithoutCheckDigit} is: {checkDigit}");
        }
    }
}

Compute PZN Number with Modulo 11

The LuhnDotNet library can be used to compute the complete Pharmazentralnummer (PZN) using the Modulo 11 algorithm. The PZN is a unique identifier for pharmaceuticals in Germany and Austria, and the last digit is a check digit calculated using the Modulo 11 algorithm. Here is an example of how to compute the complete PZN using the LuhnDotNet library:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example16
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string pznWithoutCheckDigit = "0678957";
            string pznWithCheckDigit = pznWithoutCheckDigit.ComputeMod11Number();
            //// Must be 06789572
            Console.WriteLine($"The complete PZN for {pznWithoutCheckDigit} is: {pznWithCheckDigit}");
        }
    }
}

ISBN-10 Check Digit Calculation with Modulo 11

The LuhnDotNet library can be used to compute the check digit of an ISBN-10 number using the Modulo 11 algorithm. The ISBN-10 is a 10-digit number, and the last digit is a check digit calculated using the Modulo 11 algorithm. Here is an example of how to compute the check digit of an ISBN-10 number using the LuhnDotNet library:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example17
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string isbnWithoutCheckDigit = "3-598-21508";
            char checkDigit = isbnWithoutCheckDigit.RemoveSeparators().ComputeMod11CheckDigit();
            //// Must be 8
            Console.WriteLine($"The check digit for ISBN-10 {isbnWithoutCheckDigit} is: {checkDigit}");
        }
    }
}

ISBN-10 Number Calculation with Modulo 11

The LuhnDotNet library can be used to compute the complete ISBN-10 number using the Modulo 11 algorithm. The ISBN-10 is a 10-digit number, and the last digit is a check digit calculated using the Modulo 11 algorithm. Here is an example of how to compute the complete ISBN-10 number using the LuhnDotNet library:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example18
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string isbnWithoutCheckDigit = "3-598-21508";
            string isbnWithCheckDigit = isbnWithoutCheckDigit.RemoveSeparators().ComputeMod11Number();
            //// Must be 3598215088
            Console.WriteLine($"The complete ISBN-10 for {isbnWithoutCheckDigit} is: {isbnWithCheckDigit}");
        }
    }
}

ISBN-10 Validation with Modulo 11

The LuhnDotNet library can be used to validate an ISBN-10 number using the Modulo 11 algorithm. The ISBN-10 is a 10-digit number, and the last digit is a check digit calculated using the Modulo 11 algorithm. Here is an example of how to validate an ISBN-10 number using the LuhnDotNet library:

using System;
using LuhnDotNet;
using LuhnDotNet.Algorithm.Mod11AscendingWeights;

namespace Example19
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string isbn = "3-598-21508-8";
            bool isValid = isbn.RemoveSeparators().IsValidMod11Number();
            Console.WriteLine($"The ISBN-10 {isbn} is valid: {isValid}");
        }
    }
}

CLI building instructions

For the following instructions, please make sure that you are connected to the internet. If necessary, NuGet will try to restore the xUnit packages.

Using dotnet to build for .NET 8, .NET 9 and .NET FX 4.x

Use one of the following solutions with dotnet to build LuhnDotNet:

LuhnDotNet.sln (all, see table)

The syntax is:

dotnet {restore|build|test} -c {Debug|Release} LuhnDotNet.sln

Restore NuGet packages

dotnet restore LuhnDotNet.sln

The instructions below are examples, which operate on the LuhnDotNet.sln.

Build Debug configuration

dotnet build -c Debug --no-restore LuhnDotNet.sln

Build Release configuration

dotnet build -c Release --no-restore LuhnDotNet.sln

Test Debug configuration

dotnet test -c Debug --no-restore --no-build LuhnDotNet.sln

Test Release configuration

dotnet test -c Release --no-restore --no-build LuhnDotNet.sln