NACHA Check Digit Validation and Extraction

NACHA-CheckDigit-ExampleFuncs.cs

using System;
using System.Linq;
					
public class Program
{
	public static void Main()
	{
		Func<string, int> GetCheckDigit = _routingNumber =>
			(10 - _routingNumber.Where(char.IsDigit)
							.Select((digit, index) => (digit - '0') * new[] { 3, 7, 1 }[index % 3])
							.Sum() % 10) % 10;

		Func<string, bool> IsValidCheckDigit = _routingNumber =>
		{
			return (10 - _routingNumber.Where(char.IsDigit)
							.Select((digit, index) => (digit - '0') * new[] { 3, 7, 1 }[index % 3])
							.Sum() % 10) % 10 == 0;
		};
		
		Console.WriteLine(IsValidCheckDigit("123456"));
		Console.WriteLine(IsValidCheckDigit("123456890"));
		Console.WriteLine(GetCheckDigit("123456"));
		Console.WriteLine(GetCheckDigit("1234563"));
	}
}

NACHA-CheckDigit-ExampleMethods.cs

public int GetCheckDigit(string routingNumber)
{
	if (routingNumber.Length != 8 || !routingNumber.All(char.IsDigit))
		throw new ArgumentException("Routing number must be 8 digits long.");

	int[] weights = { 3, 7, 1 };
	int sum = routingNumber.Select((digit, index) => (digit - '0') * weights[index % 3]).Sum();
	int remainder = sum % 10;
	return (10 - remainder) % 10;
}

public int GetCheckDigit2(string routingNumber)
{
	return (10 - routingNumber.Where(char.IsDigit)
					.Select((digit, index) => (digit - '0') * new[] { 3, 7, 1 }[index % 3])
					.Sum() % 10) % 10;
}

public bool IsValidCheckDigit(string routingNumber)
{
	return (10 - routingNumber.Where(char.IsDigit)
					.Select((digit, index) => (digit - '0') * new[] { 3, 7, 1 }[index % 3])
					.Sum() % 10) % 10 == 0;
}

NACHA-Epicor-VendBank-ValidationBPM.cs

// Mandatory Fields for Electronic Bank Interface

// Initialize Helpers
Func<string, bool> IsNumeric = (_inValue) =>
{
	long number;
	return Int64.TryParse(_inValue, out number);
};

Func<string, int> GetCheckDigit = _routingNumber =>
	(10 - _routingNumber.Where(char.IsDigit)
					.Select((digit, index) => (digit - '0') * new[] { 3, 7, 1 }[index % 3])
					.Sum() % 10) % 10;

Func<string, bool> IsValidCheckDigit = _routingNumber =>
{
	return (10 - _routingNumber.Where(char.IsDigit)
					.Select((digit, index) => (digit - '0') * new[] { 3, 7, 1 }[index % 3])
					.Sum() % 10) % 10 == 0;
};

// Get Vendor Row
var ttVendBankRow = ds.VendBank.FirstOrDefault(x => (x.Added() || x.Updated()) && x.Company == Session.CompanyID);

if (ttVendBankRow != null)
{
	// Get Pay Method Row
	var payMethodRow = Db.PayMethod
		.Where(x => x.Company == Session.CompanyID && x.PMUID == ttVendBankRow.PMUID)
		.Select(x => new { x.Company, x.PMUID, x.Name, x.Type, x.PMSource, x.EFTHeadUID, x.OutputFile })
		.FirstOrDefault();

	// Always Require These Good Practice
	if (ttVendBankRow.CountryNum == 0) 
	{
		throw new BLException("Pay To Country is required.");
	}
	else if (ttVendBankRow.BCountryNum == 0) 
	{
		throw new BLException("Suppliers Bank Country is required.");
	}

	// If Pay Method is Electronic Interface and contains ACH or WIRE
	if (payMethodRow.Type == 1 && (payMethodRow.Name.ToUpper().Contains("ACH") || payMethodRow.Name.ToUpper().Contains("WIRE")))
	{
		// Get Country ISO Code
		string countryISOCode = Db.Country
			.Where(c => c.Company == Session.CompanyID && c.CountryNum == ttVendBankRow.CountryNum)
			.Select(c => c.ISOCode)
			.DefaultIfEmpty("")
			.First();

		if (countryISOCode == string.Empty) 
		{
			throw new BLException("The Selected Country does not have ISO Code Configured.");
		}

		// Validate Output File for Electronic Interface is Configured
		if (string.IsNullOrEmpty(payMethodRow.OutputFile))
		{
			throw new BLException("Output File is not configured for Electronic Interface.");
		}

		//
		// WIRE PAYMENT
		//
		if (payMethodRow.Name.ToUpper().Contains("WIRE"))
		{
			// International Always Requires Swift
			if (ttVendBankRow.SwiftNum == string.Empty && countryISOCode != "US" && countryISOCode != "CA")
			{
				throw new BLException("WIRE - Bank Identifier (SWIFT) is required.");
			}
			else if (ttVendBankRow.LocalBIC == string.Empty && ttVendBankRow.SwiftNum == string.Empty)
			{
				throw new BLException("WIRE - Bank Routing Number (ABA) or Bank Identifier (SWIFT) is required.");
			}
		}
		//
		// ACH PAYMENT
		//
		else if (payMethodRow.Name.ToUpper().Contains("ACH"))
		{
			if (ttVendBankRow.LocalBIC == string.Empty)
			{
				throw new BLException("ACH - Bank Routing Number (ABA) is required.");
			}
		}

		// If Canada then Address, City, State and Zip Code are Mandatory
		if (countryISOCode == "CA"
			&& (ttVendBankRow.Address1 == string.Empty
			|| ttVendBankRow.City == string.Empty
			|| ttVendBankRow.State == string.Empty
			|| ttVendBankRow.PostalCode == string.Empty))
		{
			throw new BLException("Address, City, State and Zip Code are Mandatory for CANADA.");
		}


		// If we ever do Intermediate Bank Transfers we will need this
		/*if (ttVendBankRow["InterBankISOCountry_c"] == string.Empty
			&& (ttVendBankRow["InterBankName_c"] != string.Empty
			|| ttVendBankRow["InterBankStreet_c"] != string.Empty
			|| ttVendBankRow["InterBankBldg_c"] != string.Empty
			|| ttVendBankRow["InterBankZip_c"] != string.Empty
			|| ttVendBankRow["InterBankCity_c"] != string.Empty
			|| ttVendBankRow["InterBankState_c"] != string.Empty))
		{
			throw new BLException("Wire Intermediate Bank - Country is required.");
		}*/

		// Validate Bank Account Number, LocalBIC and SwiftNum for format if they have been specified.
		if (!string.IsNullOrEmpty(ttVendBankRow.BankAcctNumber) && (ttVendBankRow.BankAcctNumber.Length < 5 || !IsNumeric(ttVendBankRow.BankAcctNumber)))
		{
			throw new BLException("Bank Account Number is not in the correct format. It should contain at least 5 characters with only numbers.");
		}
		else if (!string.IsNullOrEmpty(ttVendBankRow.LocalBIC) && (ttVendBankRow.LocalBIC.Length < 8 || !IsNumeric(ttVendBankRow.LocalBIC)))
		{
			throw new BLException("Bank Routing Number (ABA/BIC) is not in the correct format. It should contain at least 8 characters with only numbers. US Routing Numbers should be 9 digits.");
		}
		// SWIFT should have some alpha characters not just numbers
		else if (!string.IsNullOrEmpty(ttVendBankRow.SwiftNum) && (ttVendBankRow.SwiftNum.Length < 8 || IsNumeric(ttVendBankRow.SwiftNum)))
		{
			throw new BLException("Bank Identifier (SWIFT) is not in the correct format. It should contain at least 8 characters with some alpha characters.");
		}

		// Validate Routing Number Check Digit
		if (!string.IsNullOrEmpty(ttVendBankRow.LocalBIC) && !IsValidCheckDigit(ttVendBankRow.LocalBIC))
		{
			throw new BLException("Bank Routing Number (ABA/BIC) is not valid. Check Digit is incorrect. It should be " + GetCheckDigit(ttVendBankRow.LocalBIC));
		}

		// Bank Account Number should not be the same as the Routing Number
		if (ttVendBankRow.BankAcctNumber == ttVendBankRow.LocalBIC)
		{
			throw new BLException("Bank Account Number should not be the same as the Bank Routing Number.");
		}
	}
}