Random rnd = new Random();
int[] dizi = new int[7];
for (int i = 0; i < dizi.Length; i++) {
    int rnum = rnd.Next(1, 49);
    for (int j = 0; j < dizi.Length; j++)
    {
        if (dizi[j] ==rnum)
        {
            continue;
        }
    }

    dizi[i] = rnum;

}
for (int j = 0; j < dizi.Length; j++)
{
    Console.WriteLine(dizi[j]); 
}
Console.ReadKey();