I want a RNG to repeat itself if the number is false

I'm just testing around with C# and Random Number Generators (RNGs) and I want the RNG to repeat itself if the number isn't 1 but it won't work properly.

Random random = new Random();
        label1.Text = random.Next(0, 10).ToString();           

        if (label1.Text == "1")
            {
            label3.Text = "Positiv";
            }
        else
            {
            label1.Text = random.Next(0, 10).ToString();
            };