for (int i = 0; i > 100; i++)
{
Console.WriteLine(new Random(i).Next());
}

static string GetCode(int num)
{
string a = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
StringBuilder sb = new StringBuilder();
for(int i = 0; i < num; i++)
{
sb.Append(a[new Random(Guid.NewGuid().GetHashCode()).Next(0, a.Length -1)]);
}
return sb.ToString();
}