C# IndexOutOfRangeException when calling Array.GetLength(1) for a 2D Array

Question

here is the code, I noticed that the Getlength method returns 0 but I think its normal as the for loop wont go further than 0.. I've written

int yy = tile.GetLength(1);

and it throws the same exception as the code under :

 TileData[][] tile = GameMain.Level.getCollisionTiles();

        Rectangle tileRectangle;
        for(int x = 0; x <= tile.GetLength(0); x++)
        {
            for (int y = 0; y <= tile.GetLength(1); y++) //EXCEPTION THROWN HERE AT GETLENGTH !!!!
            {
                tileRectangle = tile[x][y].Target;
                if (tileRectangle.Contains(m_hitbox)) //Si il y a collision
                {
                    if ((m_hitbox.X + m_hitbox.Width) > tileRectangle.X) //si le joueur percute par la gauche
                    {
                        m_hitbox.X--;
                    }
                    else if (m_hitbox.X < (tileRectangle.X + tileRectangle.Width)) //Droite
                    {
                        m_hitbox.X++;
                    }
                    if ((m_hitbox.Y + m_hitbox.Height) > tileRectangle.Y) //si le joueur percute par le haut
                    {
                        m_hitbox.Y--;
                    }
                    else if (m_hitbox.Y < (tileRectangle.Y + tileRectangle.Height)) //Bas
                    {
                        m_hitbox.Y++;
                    }
                }
            }
        }

EDIT: I got it working by getting the tile info from the map object, but now it throws NullReferenceException

        TileData[][] tile = GameMain.Level.getCollisionTiles();
        int xMax = GameMain.Level.getMapHeight();
        int yMax = GameMain.Level.getMapWidth();

        for (int x = 0; x <= xMax; x++)
        {
            for (int y = 0; y <= yMax; y++)
            {
                Rectangle tileRectangle = tile[x][y].Target; //THIS LINE FAILS !!!!
                if (tileRectangle.Contains(m_hitbox)) //Si il y a collision
                {
                    if ((m_hitbox.X + m_hitbox.Width) > tileRectangle.X) //si le joueur percute par la gauche
                    {
                        m_hitbox.X--;
                    }
                    else if (m_hitbox.X < (tileRectangle.X + tileRectangle.Width)) //Droite
                    {
                        m_hitbox.X++;
                    }
                    if ((m_hitbox.Y + m_hitbox.Height) > tileRectangle.Y) //si le joueur percute par le haut
                    {
                        m_hitbox.Y--;
                    }
                    else if (m_hitbox.Y < (tileRectangle.Y + tileRectangle.Height)) //Bas
                    {
                        m_hitbox.Y++;
                    }
                }
            }
        }

Sorry to ask you this question in the same topic, but i think you can help me resolving it fast.

It's not a 2D array. TileData[][] is not TileData[,]

Adriano Repetti
– Adriano Repetti

2013-11-18 14:47:11 +00:00
Commented Nov 18, 2013 at 14:47 — Adriano Repetti
– Adriano Repetti, Commented Nov 18, 2013 at 14:47

Adriano Repetti · Accepted Answer · 2013-11-18 16:14:48Z

8

It's not a 2D array. TileData[][] is a jagged array, TileData[,] is a 2D array then, in your case, GetLength(1) will always fail because tile has only one dimension.

EDIT
What to do to solve this? You can change tile from [][] to [,] (for example) and keep everything else as is (how getCollisionTiles() works?) or you may update your code to get right size from jagged array, like this:

for (int y = 0; y < tile[x].GetLength(0); y++)

BTW you may even replace GetLength(0) with a simple Length:

for(int x = 0; x < tile.Length; x++)
{
    for (int y = 0; y < tile[x].Length; y++)

Final note: for 0 based arrays Length is not inclusive for index so x <= tile.Length must be replaced with x < tile.Length.

edited Nov 18, 2013 at 16:14

answered Nov 18, 2013 at 14:47

Adriano Repetti

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9 Comments

stalker2106 Over a year ago

thanks for answering, but then how am i supposed to get the length of the second [] in array ?

Nico Over a year ago

@user3005141 initilize your array that way: TileData[,] tile = GameMain.Level.getCollisionTiles();

Adriano Repetti Over a year ago

@user3005141 it depends what getCollisionTiles() returns...you may change your array to [,] instead of [][] or you can use a for to initialize each element (see updated answer).

stalker2106 Over a year ago

The getCollisionTiles() returns a [][] array, but i havent written it, it depends of a framework, and when i try to convert it of course it says : Erreur 3 Unable to convert type 'FuncWorks.XNA.XTiled.TileData[][]' to 'FuncWorks.XNA.XTiled.TileData[,]'

Servy Over a year ago

@user3005141 There isn't one array for your second dimension. There are N different arrays for the inner dimension, all potentially with a different length. If you happen to know that they're all the same you can just pick one, but if they aren't all the same then you need to deal with that when accessing items.

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