using System;

public class Program

{   

    public void Main()

    {       

        //How many ID numbers would you like to generate?

        int count = 10;

        for (int i = 0; i < count; i++)

        {

            string fakeID = returnFullLengthID();

            Console.WriteLine(fakeID);

        }

    }

    private string returnFullLengthID()

    {

        //Generate a random date

        DateTime start = new DateTime(1900, 01, 01);

        int range = (DateTime.Today - start).Days; 

        start = start.AddDays(RandomNumber(0, range));

        string date = start.ToString("yyMMdd");

        //Generate a random gender code

        string genderCode = RandomNumber(0, 9999).ToString("0000"); 

        //Generate a random citizenship status

        string citizenship = RandomNumber(0, 2).ToString();

        //Generate a random race code

        string raceCode = 8.ToString(); //gen.Next(0, 7).ToString(); -- no longer used      

        //Put it all together in a 12 digit temp id

        string myString = string.Format("{0}{1}{2}{3}", date, genderCode, citizenship, raceCode);

        //For every 'even' indexed digit, first take it, and double it.

        //If the outcome is greater than 10, treat it as two numbers that get added together.

        //For every 'odd' indexed digit, use it as is.

        //Add everything together

        int digit1 = int.Parse(myString.Substring(0,1));

        int digit2 = int.Parse(myString.Substring(1,1)) *2;

        digit2 = SplitAndAddNumbersTogether(digit2);

        int digit3 = int.Parse(myString.Substring(2,1));

        int digit4 = int.Parse(myString.Substring(3,1)) *2;

        digit4 = SplitAndAddNumbersTogether(digit4);

        int digit5 = int.Parse(myString.Substring(4,1));

        int digit6 = int.Parse(myString.Substring(5,1)) *2;

        digit6 = SplitAndAddNumbersTogether(digit6);

        int digit7 = int.Parse(myString.Substring(6,1));

        int digit8 = int.Parse(myString.Substring(7,1)) *2;

        digit8 = SplitAndAddNumbersTogether(digit8);

        int digit9 = int.Parse(myString.Substring(8,1));

        int digit10 = int.Parse(myString.Substring(9,1)) *2;

        digit10 = SplitAndAddNumbersTogether(digit10);

        int digit11 = int.Parse(myString.Substring(10,1));

        int digit12 = int.Parse(myString.Substring(11,1)) *2;

        digit12 = SplitAndAddNumbersTogether(digit12);

        int total = digit1 + digit2 + digit3 + digit4 + digit5 + digit6 + 

            digit7 + digit8 + digit9 + digit10 + digit11 + digit12;

        //Determine the missing digit

        int missingDigit = 10 - (total % 10);

        //Return the fake ID number 

        if (missingDigit == 10)

            return myString + "0";

        else

            return myString + missingDigit.ToString();  

    }

    private int SplitAndAddNumbersTogether(int digitToCheck)

    {

        if (digitToCheck >= 10)

        {

            int digit1 = 1;

            int digit2 = digitToCheck - 10;

            digitToCheck = digit1 + digit2;

        }

        return digitToCheck;

    }

    private static readonly Random random = new Random(); 

    private static readonly object syncLock = new object(); 

    public static int RandomNumber(int min, int max)

    {

        lock(syncLock) { // synchronize

            return random.Next(min, max);

        }

    }

}