generate random numbers with no repeat in c#

Question

How can I generate random numbers with no repeat in C#. I have one array and I want to fill every room with random numbers from 0 to 9. Each room shoud have diffrent numbers

Answer 1

    public Form1()
    {
        InitializeComponent();
    }
    int A, B;
    string Output;
    private void Form1_Load(object sender, EventArgs e)
    {
        for (int i = 0; i < 20; i++)
        {
            while (A == B)
            {
                Random r = new Random();
                A = r.Next(1, 6);
            }
            Output = Output + A;
            B = A;
        }
        textBox1.Text = Output;
    }

Output: 24354132435213245415 (not repeating)