Generate N random and unique numbers within a range

Question

What is an efficient way of generating N unique numbers within a given range using C#? For example, generate 6 unique numbers between 1 and 50. A lazy way would be to simply

Answer 1

generate unique random nos from 1 to 40 :

output confirmed :

class Program

{
    static int[] a = new int[40];
    static Random r = new Random();
    static bool b;
    static void Main(string[] args)
    {
        int t;
        for (int i = 0; i < 20; i++)
        {
        lab:  t = r.Next(1, 40);
            for(int j=0;j<20;j++)
            {

                if (a[j] == t)
                {
                    goto lab;
                }
            }

            a[i] = t;
            Console.WriteLine(a[i]);



        }
        Console.Read();
    }


}

sample output :

7 38 14 18 13 29 28 26 22 8 24 19 35 39 33 32 20 2 15 37