static void Main(string[] args)
    {
        FileStream fStream = new FileStream("test.txt", FileMode.Open, FileAccess.Read);
        StreamReader inFile = new StreamReader(fStream);

        string inputRecord = "";
        string[] fields;
        int[] ageData = new int[1000];
        string[] genderData = new string[1000];
        string[] maritalData = new string[1000];
        int[] districtData = new int[1000];
        int[] countDist = new int[23];
        int[] ageGroup = new int[5];

        inputRecord = inFile.ReadLine();

        int i = 0;
        while (inputRecord != null)
        {
            fields = inputRecord.Split(',');

            ageData[i] = int.Parse(fields[0]);
            genderData[i] = fields[1];
            maritalData[i] = fields[2];
            districtData[i] = int.Parse(fields[3]);

            if (ageData[i] > 0 && ageData[i] <= 18)
            {
                ageGroup[0] = ageGroup[0] + 1;
            }
            if (ageData[i] > 18 && ageData[i] <= 30)
            {
                ageGroup[1] = ageGroup[1] + 1;
            }
            if (ageData[i] > 30 && ageData[i] <= 45)
            {
                ageGroup[2] = ageGroup[2] + 1;
            }
            if (ageData[i] > 45 && ageData[i] <= 64)
            {
                ageGroup[3] = ageGroup[3] + 1;
            }
            if (ageData[i] >= 65)
            {
                ageGroup[4] = ageGroup[4] + 1;
            }

            i++;

            inputRecord = inFile.ReadLine();
        }
        Console.WriteLine("This Program takes census data from a file and lists residents by age group and district");
        Console.WriteLine("Please ensure the file is formatted correctly! age,gender (M/F),marital status   (M/S), and district");
        for (int x = 1; x <= 22; x++)
            for (int y = 0; y < districtData.Length; y++)
                if (districtData[y] == x)
                    countDist[x]++;

        for (int x = 1; x <= 22; x++)
            Console.WriteLine("District   " + x + "   has   " + countDist[x] + "   citizens");



        Console.WriteLine("------Amount of Residents per Age Group--------");
        Console.WriteLine("Age Group 18 & under = {0}", ageGroup[0]);
        Console.WriteLine("Age Group 18-30 = {0}", ageGroup[1]);
        Console.WriteLine("Age Group 31-45 = {0}", ageGroup[2]);
        Console.WriteLine("Age Group 46-64 = {0}", ageGroup[3]);
        Console.WriteLine("Age Group 65 & over = {0}", ageGroup[4]);
    }

if (ageData[i] > 0 && ageData[i] <= 18)
{
    ageGroup[0] = ageGroup[0] + 1;
}
if (ageData[i] > 18 && ageData[i] <= 30)
{
    ageGroup[1] = ageGroup[1] + 1;
}

if (ageData[i] > 0 && ageData[i] <= 18)
{
    ageGroup[0] = ageGroup[0] + 1;
}
else if (ageData[i] <= 30) //I removed the "ageData[i] > 18 && "
{
    ageGroup[1] = ageGroup[1] + 1;
}

string[] contents = System.IO.File.ReadAllLines(@"c:pathtofile.txt");

foreach(string line in contents)
{
    fields = line.Split(',');
}

for(int lineNumber = 0; lineNumber < contents.Length; lineNumber++
{
    fields = contents[lineNumber].Split(',');
    //etc.
}

int[] ageData = new int[1000];
ageData[i] = int.Parse(fields[0]);

List<int> ageData = new List<int>();
ageData.Add(int.Parse(fields[0]));
//you have to add an int to the list before you can use it

const int COLUMN_AGE = 0;
const int ARRAY_SIZE = 1000;
//etc.

int[] ageData = new int[ARRAY_SIZE];
ageData[i] = int.Parse(fields[COLUMN_AGE]);
//etc.

Console.WriteLine("District   " + x + "   has   " + countDist[x] + "   citizens");

Console.WriteLine("District   {0}   has   {1}   citizens", x, countDist[x]);

for (int x = 1; x <= 22; x++)
    for (int y = 0; y < districtData.Length; y++)
        if (districtData[y] == x)
            countDist[x]++;

for (int districtCount = 1; districtCount <= 22; districtCount++)
{
    for (int districtNumber = 0; districtNumber < districtData.Length; districtNumber++)
    {
        if (districtData[districtNumber] == districtCount)
        {
            countDist[districtCount]++;
        }
    }
}

public class Record
{
    public int Age { get; set; }
    public string Gender { get; set; }
    public string MaritalStatus { get; set; }
    public int District { get; set; }
}

var records = new List<Record>();
var inputRecord = inFile.ReadLine();

while (inputRecord != null)
{
    var fields = inputRecord.Split(',');
    var currentRecord = new Record()
    {
        Age = int.Parse(fields[0]),
        Gender = fields[1],
        MaritalStatus = fields[2],
        District = int.Parse(fields[3])
    };

    records.Add(currentRecord);
    //...
}

using (var fStream = new FileStream("test.txt", FileMode.Open, FileAccess.Read))
{
    using (var inFile = new StreamReader(fStream))
    {
        //Work with the file here
        //...
    } //inFile.Dispose() happens here automatically.
} //fStream.Dispose() happens here automatically.

for (int x = 1; x <= 22; x++)
        for (int y = 0; y < districtData.Length; y++)
            if (districtData[y] == x)
                countDist[x]++;