[ Random numbers for dice game ]

Possible Duplicate:
random string generation - two generated one after another give same results

I am writing a simple dice game for windows phone 7, that involves rolling two dice at the same time. Here is my Dice Roll Code:

 private int DiceRoll()
    {
        int result;
        Random rnd = new Random();

        result = rnd.Next(1, 7);
        return result;
    }

I then have this code that rolls the dice when a button is clicked:

   private void roll_Click(object sender, RoutedEventArgs e)
    {
        roll1 = DiceRoll();
        roll2 = DiceRoll();}

My problem is that both die get the same result.

Any idea how I can get a rolling algorithm that will usually return different results, but occasionally return the same?

Answer 1

The default seed for Random is based on the current time. To quote the documentation,

As a result, different Random objects that are created in close succession by a call to the default constructor will have identical default seed values and, therefore, will produce identical sets of random numbers. This problem can be avoided by using a single Random object to generate all random numbers.

That is exactly what you should do: create one instance of Random and use it to generate all your random numbers.

Answer 2

The clear majority of 'random number' tools I've seen fail badly if you allocate two or more random objects in a single application. You're allocating a new Random object for every invocation, and each time they are going to be seeded with something pretty weak, and maybe even identical seeds.

So, generate a single Random object and use it over the life of your application.

Answer 3

You need to keep one Random object around and reuse it; every time you create a new Random object, you effectively reset the sequence of numbers to begin in the same place. Store the Random object as a member variable someplace. You'll also want to seed it with a different value each time you run the program -- for example, a value based on the system clock time.