Question

System.Random generator = new Random(DateTime.Now.Millisecond);
int[] lotteryNumber = new int[7];

Console.WriteLine("Your lottery numbers: ");
for (int i = 0; i<7; i++)
{
    lotteryNumber[i] = generator.Next(1, 37);
    Console.Write("{0} ",lotteryNumber[i]);
}
Console.ReadLine();

I need to make a program that prints 7 lottery numbers, but without duplicates. The code above prints 7 random numbers in the range of (1-37), but duplicates appaer. I need a way to prevent duplicate numbers from appearing.

Answer 1

The simplest approach IMO would be to generate a sequence of all the possible numbers (i.e. 1-37), shuffle the collection, then take the first seven results.

Searching on Stack Overflow for “Fisher-Yates shuffle C#” will find lots of examples.

In fact, you could modify the Fisher-Yates shuffle to yield results as you took them, so you could write a method such as:

var numbers = Enumerable.Range(1, 37).Shuffle().Take(7).ToList();