c# 一段生成6位不重復的隨機數字碼存8萬個

static void Main(string[] args)
{
ArrayList al = new ArrayList();
Random rd = new Random();
int count = 0;
bool sign = true;
while (sign)
{

int end = 999999;
int begin = 100000;
Int64 k = rd.Next(begin, end);
Int64 i = k + 99;
if (!al.Contains(i))
{
count++;
al.Add(i);
// Console.WriteLine(i.ToString());
Write(i.ToString());
}
if (count == 80000)
{ sign = false; }
}
Console.WriteLine(al.Count.ToString());
Console.ReadKey();

// GenerateRandomCode(6);
}
public static void Write(string text)
{
FileStream fs = new FileStream(@"log.txt", FileMode.Append);
StreamWriter sw = new StreamWriter(fs, Encoding.Default);
sw.WriteLine(text);
sw.Close();
fs.Close();
}
/// <summary>
///生成制定位數的隨機碼（數字）
/// </summary>
/// <param name="length"></param>
/// <returns></returns>
public static string GenerateRandomCode(int length)
{
var result = new StringBuilder();
for (var i = 0; i < length; i++)
{
var r = new Random(Guid.NewGuid().GetHashCode());
result.Append(r.Next(0, 10));
}
return result.ToString();
}