How to randomly generate 1000 sequences of 6 digit number

I want to generate 1000 number randomly and put the result in a rich text box ,but the result I got from my code is just one number appearing in the rich text box !!

 private Random _random = new Random();
        int min = 000000;
        int max = 999999;
        string s;  
 private void Form1_Load(object sender, EventArgs e)
        {
            for (int i = 0; i < 1000; i++)
            {
                s = _random.Next(min, max).ToString("D6") + "\n";
            }
            richTextBox1.Text = s;
        }