C# Update few Picture Boxes at the same time

Question

I have 5 Picture Boxes in my application, and I update them at the same time. I want them to display 5 different Images and my programs code is right, but for some reason the picture boxes show all the same image...

Here's the code:

private System.Drawing.Bitmap DiceOne;
private System.Drawing.Bitmap DiceTwo;
private System.Drawing.Bitmap DiceThree;
private System.Drawing.Bitmap DiceFour;
private System.Drawing.Bitmap DiceFive;
private System.Drawing.Bitmap DiceSix;

public void Prepare()
{
    for (int i = 0; i < 5; i++)
        Dices[i] = new Dice();

    DiceOne = Properties.Resources.Würfel_1;
    DiceTwo = Properties.Resources.Würfel_2;
    DiceThree = Properties.Resources.Würfel_3;
    DiceFour = Properties.Resources.Würfel_4;
    DiceFive = Properties.Resources.Würfel_5;
    DiceSix = Properties.Resources.Würfel_6;
}

public void Roll()
{
    foreach (Dice dice in Dices)
        dice.RollTheDice();

    View.SuspendLayout();
    View.diceOnePictureBox.Image = DiceNumberToBmp(Dices[0].GetLastRolled());
    View.diceOnePictureBox.Update();
    View.diceTwoPictureBox.Image = DiceNumberToBmp(Dices[1].GetLastRolled());
    View.diceOnePictureBox.Update();
    View.diceThreePictureBox.Image = DiceNumberToBmp(Dices[2].GetLastRolled());
    View.diceOnePictureBox.Update();
    View.diceFourPictureBox.Image = DiceNumberToBmp(Dices[3].GetLastRolled());
    View.diceOnePictureBox.Update();
    View.diceFivePictureBox.Image = DiceNumberToBmp(Dices[4].GetLastRolled());
    View.diceOnePictureBox.Update();
    View.ResumeLayout(false);
}

private System.Drawing.Bitmap DiceNumberToBmp(int number)
{
    switch(number)
    {
        case 1:
            return DiceOne;
        case 2:
            return DiceTwo;
        case 3:
            return DiceThree;
        case 4:
            return DiceFour;
        case 5:
            return DiceFive;
        case 6:
            return DiceSix;
        default:
            return null;
    }
}

I've read some familier posts on the internet before, and tried to solve with with SuspendLayout, ResumeLayout, Updating the PictureBox.... Nothing worked for me.

My Dice class:

using System;

namespace KniffelGUI.Model
{
    public class Dice
    {

        private int LastRolled;

        public Dice()
        {
            RollTheDice();
        }

        public Dice(int fakeRoll)
        {
            LastRolled = fakeRoll;
        }

        public int RollTheDice()
        {
            LastRolled = new Random().Next(6) + 1;

            return LastRolled;
        }

        public int GetLastRolled()
        {
            return LastRolled;
        }

    }
}

Oh okay, didn't notice that, changed it to the respective names, but it still doesn't work. — Michael, Dec 19 '19 at 13:17
@BarryO'Kane in the GetLastRolled() I just return a local variable, but in Dice.RollTheDice() I am using Random, yes. — Michael, Dec 19 '19 at 13:18
Can you post that code? Sounds like you may be victim of the Random default constructor problem https://csharpindepth.com/Articles/Random — Barry O'Kane, Dec 19 '19 at 13:23
@BarryO'Kane the Random works, it returns me numbers from 1 to 6. It's just the problem with the Picture Boxes — Michael, Dec 19 '19 at 13:25
What is `View.`? I don't see that declared anywhere. Do the pictureboxes change at all?...but all change to the same one? Or do they just never change? — Idle_Mind, Dec 19 '19 at 13:32
@Idle_Mind View is just my Main Form. And in the code I posted, you can see the Picture boxes change to different pictures depending on the integer the Random returns. — Michael, Dec 19 '19 at 13:34
You didn't answer the question. I can see that your code is **attempting** to change the pictureboxes. What are you actually seeing, though? Do they change at all? I also think we need to see your `Dice()` class... — Idle_Mind, Dec 19 '19 at 13:43
@Idle_Mind All picture boxes update, the only problem is that they are showing all the same picture. I'm gonna edit the main post and add the Dice class — Michael, Dec 19 '19 at 13:47
Well, we don't see a problem in the code you've posted...need to start looking elsewhere. Show us how you declare and set `View`, and your `Dice()` class. — Idle_Mind, Dec 19 '19 at 13:48
@Idle_Mind I transmit the MainView Form Class in the Constructor of the class you see in my code(MainController.cs) — Michael, Dec 19 '19 at 13:51

score 1 · Accepted Answer · answered Dec 19 '19 at 14:02

The problem is in your Dice class, as suggested earlier by Barry O'Kane.

Change it to:

public class Dice
{

    private int LastRolled;
    private static Random R = new Random();

    public Dice()
    {
        RollTheDice();
    }

    public Dice(int fakeRoll)
    {
        LastRolled = fakeRoll;
    }

    public int RollTheDice()
    {
        LastRolled = R.Next(6) + 1;
        return LastRolled;
    }

    public int GetLastRolled()
    {
        return LastRolled;
    }

}

Your symptom was occurring because of this line:\

LastRolled = new Random().Next(6) + 1;

When you create an instance of Random with the default constructor, it uses the current time as the seed. When you create multiple instances in rapid succession, they end up with the same seed and therefore won't get different numnbers.

By declaring it as static, all instances of your class will use the same Random instance and get a different number upon each call.

C# Update few Picture Boxes at the same time

1 Answers1