Program that creates random numbers from 1 to "n", without repeating, in .NET c# and store them in a array of size [n]

Well, I've been coding this program that has the objective to create random numbers, and then store them in an array (linhas[n]), but I don't want them to repeat. I started by doing a for cicle (int i = 0; i < n; i++) and inside it I wrote that an variable a (int a) was equal to a random number generated from the random function (r). Then I compared if "a" already existed in the array, using "bool b = Array.Exists(linhas, elements => elements == a);", then wrote that if "b" was true it would decrease the "i" value by one, to repeat the same i cicle, doing linhas[i] = a if "b" was false. Then it would write the elements of the array. The problem that I'm getting is that when I oppen the program and write the value of "n" the program just doesn't do nothing, just a black screen. I already checked and if I put the value of "n" = 1, the program generates just one number, number 1. But if I put "n" = 2 it just stops. If anyone understood what I said here and could help me, please just throw some tips!

The code here:

static void Main(string[] args)
    {
        int n;
        Console.Write("Escreva o número de linhas a aparecer: ");
        n = Convert.ToInt32(Console.ReadLine());
        int[] linhas = new int[n];
        var r = new Random();
        for (int i = 0; i < n; i++) 
        {
            int a = r.Next(1, n);
            bool b = Array.Exists(linhas, elements => elements == a);
            if (b == true)
            {
                i--;
            }
            else
            {
                linhas[i] = a;
            }
        }
        Console.WriteLine("");
        for (int i = 0; i < n; i++)
        {
            Console.WriteLine(linhas[i]);
        }
        Console.Read();
    }