Create Set Of 10 Random Numbers Every Time Page Loads?

I am trying to create a Question Bank application for one of our clients. What is the main challenge I am facing is a typical demand from the client. What they want is : Whenever users open this site a set of random numbers(range say 1 to 20) should be generated and questions with the QuestionID(column in a table in Database) according to the numbers would be displayed in the page. I have done it to some extent but, still not satisfied with it.

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
int[] n = new int[10];
int rn;
bool Check = true;
int[] n1 = new int[10];
Random rand = new Random();
n1[0] = rand.Next(1, 21);
for (int i = 1; i < 10; i++)
{
rn = rand.Next(1, 21);
for (int j = 0; j < n1.Length; j++)
{
if (n1[j] == rn)
{
Check = false;
break;
}
else
continue;
}
if (Check == true)
n1[i] = rn;
}
for(int i=0;i<10;i++)
Response.Write(n1[i] + " ");
}
}

Here are some O/Ps : 11 13 14 4 16 0 0 0 0 0 (1st load)
5 9 8 1 0 0 0 0 0 0 (after refreshing the page)
16 10 20 6 8 17 11 7 0 0 (after refreshing again)

I want that, all these digits in each refresh should be unique(which is comming) but all set should 10 digits(this is not happening).