public string ToMachineForm()
{
string accNumber = string.Empty;
if (AccountNumber.Length < 8 || AccountNumber.Length > 14 || AccountNumber[6] != '-')
{
return("Invalid account number. Proper account number is 8-14 numbers long and contains dash after first 6 numbers");
}
accNumber = AccountNumber.Remove(6, 1);
if (!accNumber.All(Char.IsDigit))
{
return("Invalid account number. No letters allowed");
}
if (accNumber[0].Equals('4') || accNumber[0].Equals('5'))
{
while (accNumber.Length < 14)
{
accNumber = accNumber.Insert(7, "0");
}
}
else
{
while (accNumber.Length < 14)
{
accNumber = accNumber.Insert(6, "0");
}
}
string checksum = HasValidChecksum(accNumber);
if (checksum == accNumber.Substring(accNumber.Length - 1))
{
Message = "Account number is valid. Checksum " + checksum + " is equal to the last digit.";
}
else
{
Message = "Account number is invalid. Checksum " + checksum + " is not equal to the last digit.";
}
return("Account number " + AccountNumber + " in machine form is: " + accNumber);
}
