Question

For a part of a program i need the following 2 methods.

The first method listed will generated a random number.
where the 2nd method will “call” this method to fill the array.

The array has a max. number of elements defefined on 100 (and all the random generated numbers should be between 1-100).

The problem is i never get random numbers generated. (either i get 100 x the same value, 3 random numbers divided over the 100 max. elements of the array, or the same value 100 times all over again).

The problem should be in the first method, but i cannot seem to figure out the problem.
Been staring at this for quite some time now…

The problem should be with the return, cause it DOES create random generated numbers. But how do i return the generated value every time? (the int method has to be called with the 3 parameters).

        private int ValidNumber(int[] T, int X, int Range)
    {
        for (byte I = 0; I < T.Lenght; I++)
        {
            Random RndInt = new Random();
            X = RndInt.Next(1, Range+1);
        }
        return X; 

    }/*ValidNumber*/


  public void FillArray(int[] T, int Range)
    {
        for (byte I = 0; I < T.Length; I++)
        {
            T[I] = ValidNumber(T, I, Range);
        }

    }/*FillArray*/

Console code:

public void ExecuteProgram()
    {
        ClsBereken Ber = new ClsBereken();

        //const byte Range = 100;
        const int Max = 100;
        int[] T = new int[Max];

        Ber.FillArray(T, Max);
        DisplayArray(T);

    }/*ExecuteProgram*/

    private void DisplayArray(int[] T)
    {
        for (byte i = 0; i < T.Length; i++)
        {
            Console.Write("{0,4} ", T[i]);
        }
        Console.WriteLine();
    }/*DisplayArray*/

Any help alot appreciated.
Kind Regards.

Answer 1

Re-use the Random instance. NOTE I’ve edited this to show passing the Random instance down, but I’m really not sure what ValidNumber is trying to do – it looks like it is juts burning up CPU cycles? I would suggest you can remove ValidNumber completely (and just use the next value from the Random in FillArray), but presumably you are trying to do something here – I’m just not sure what!

private int ValidNumber(int[] T, int X, int Range, Random random)
{
    for (byte I = 0; I < T.Lenght; I++)
    {
        X = random.Next(1, Range+1);
    }
    return X; 

}/*ValidNumber*/


public void FillArray(int[] T, int Range)
{
    Random random = new Random();
    for (byte I = 0; I < T.Length; I++)
    {
        T[I] = ValidNumber(T, I, Range, random);
    }

}/*FillArray*/

When you create a Random, it is “seeded” using the system clock, but this is rounded heavily. If you create lots of Random in a tight loop, they all get the same “seed”, so they all create the same next number.

If necessary you could move the Random further out (if you have other loops), or make it static (but if you do that you need to worry about synchronization too).