CODEWITHSUNDEEP
c#multidimensional-array
user2702899
user2702899

Reputation: 23

C# multidimensional array value changes unexpectedly

Hello i have a realy strange behavior in this piece of code:

public class IGraphics
{
    public  int[,] screen;

    private int[,] world;
    private int[,] entitys;
    private int[,] buffer;

    private int screenW;
    private int screenH;
    public IGraphics(int screenW, int screenH) {

        this.screenH = screenH;
        this.screenW = screenW;
        screen = new int[screenW + 1, screenH];
        buffer = new int[screenW + 1, screenH];


    }
    public void loadWorld(int[,] world) {
        this.world = world;
    }
    public void clear() {
        screen = new int[screenW + 1, screenH];
        world = new int[screenW, screenH];
        for (int y = 0; y < world.GetLength(1); y++) {
            for (int x = 0; x < world.GetLength(0); x++) {
                world[x, y] = 0;

            }

        }

    }

    private void loadScreen() {


    }
    private void updateEntitys()
    {
        entitys = new int[screenW, screenH];
        List<GameObject> EntRow = Common.world.getEntitys();
        for (int i = 0; i < EntRow.Count(); i++)
        {
            entitys[EntRow[i].x, EntRow[i].y] = EntRow[i].Icon;
        }

    }
    public void draw() {

        updateEntitys();
        for (int y = 0; y < screen.GetLength(1); y++)
        {
            for (int x = 0; x < screen.GetLength(0) - 1; x++)
            {
                if (entitys[x, y] == 0)
                {
                    screen[x, y] = world[x, y];
                }
                else
                {
                    screen[x, y] = entitys[x, y];

                }
            }

            screen[screen.GetLength(0) - 1, y] = 123;

        }
        if (buffer.Cast<int>().SequenceEqual(screen.Cast<int>()))
        {
            return;
        }
        Console.Clear();
        buffer = screen;
        for (int y = 0; y < screen.GetLength(1); y++) {
            for (int x = 0; x < screen.GetLength(0); x++) {
                if (screen[x, y] == 123)
                {
                    Console.WriteLine();
                }
                else {
                    Console.Write(objectStore.getIcon(screen[x, y]));
                }
            }

        }

    }

}

the problem comes in the Draw() function where i set the value of the screen[,] array for some reason it also change the value of the buffer[,] array before the control also tried moving the buffer[,] in a seperate class but i had the same problem.

Someone as an explanation?

Upvotes: 0

Views: 85

Answers (3)

Les
Les

Reputation: 10605

See the other answers for possible reasons for your problem. However, the following code shows that changing screen[] does not change buffer[]. This kind of effort on your part would allow you to focus your investigation elsewhere. The principle is to first simply.

    int counter = 1;
    public void draw()
    {

        for (int y = 0; y < screen.GetLength(1); y++)
        {
            for (int x = 0; x < screen.GetLength(0) - 1; x++)
            {
                screen[x, y] = counter++;
            }
            screen[screen.GetLength(0) - 1, y] = 123;
        }
        if (buffer.Cast<int>().SequenceEqual(screen.Cast<int>()))
        {
            MessageBox.Show("Help!");
            return;
        }
        // check again
        for (int y = 0; y < screen.GetLength(1); y++)
        {
            for (int x = 0; x < screen.GetLength(0) - 1; x++)
            {
                if (screen[x, y] == buffer[x, y])
                {
                    MessageBox.Show("Help two!");
                    return;
                }
            }
        }

Upvotes: 0

Eric
Eric

Reputation: 940

When you assign a reference variable to another variable, you copy the pointer to that variable, instead of copying the content, so what you end up with is two variables that point to the same array.

Try to instead copy the array using Clone or copy or something. I think its screen.CopyTo

screen.CopyTo(buffer, 0);

Upvotes: 1

Christos
Christos

Reputation: 53958

If you look at the body of the method called draw, you will notice this assignment:

buffer = screen;

This is might the cause of the change you noticed.

Upvotes: 1

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