Accessing one dimension of multidimensional array

Question

I have a multidimensional array which looks like this:

public static int[,] GameObjects = new int[,]
{
    //Type,X,Y,Width,Height
    {0,50,50,10,100},
    {1,50,150,10,20}
};

I'm trying to access one "row" of values and store them into a variable within a for loop:

 for (int i = 0; i < gameObjectData.Length; i++)
 {
     int[] g = gameObjectData[i];
 }

I want g to store the first array's values, so in the first loop g should store 0,50,50,10,100. The code gives the error Wrong number of indices inside []; expected 2

`int[,]` and `int[][]` are not the same. I forget the specifics (looking up now, I find it , I'll post an answer) — Flater, Apr 30 '15 at 13:10
`int[,]` is not the same as `int[][]`. You need to copy the values of one row to a new array. — Dennis_E, Apr 30 '15 at 13:10
Look at this http://stackoverflow.com/questions/5132397/fast-way-to-convert-a-two-dimensional-array-to-a-list-one-dimensional — Dmitry Bychenko, Apr 30 '15 at 13:20

score 3 · Answer 1 · edited May 23 '17 at 12:14

3

You get this error because you try to use a multidimensional array as if it was a jagged array.

Change

int[,]

to

int[][]

and you will be fine.
Read here about the differences between these types of arrays.

edited May 23 '17 at 12:14

Community

1
1

answered Apr 30 '15 at 13:10

Zohar Peled

79,642
10
69
121

Servy · Accepted Answer · 2015-04-30T13:22:49.737

There is no exposed mechanism of a two dimensional array to get a single dimensional array out of it.

If you have a jagged array then it's possible:

int[][] array;
//populate array
int[] row = array[1];

If you need to have a multi-dimensional array then the best you could do is create a class to hold onto a two dimensional array and a row number and expose an indexer to access items in that row; it could appear similar to an array, but it wouldn't actually be one.

Something like this would give you the bare bones; if you wanted to make the type extend IList<T> you could do that as well.

public class ArrayRow<T> : IEnumerable<T>
{
    private T[,] array;
    private int index;
    public ArrayRow(T[,] array, int index)
    {
        this.array = array;
        this.index = index;
    }

    public T this[int i]
    {
        get { return array[index, i]; }
        set { array[index, i] = value; }
    }

    public int Count { get { return array.GetLength(1); } }

    public IEnumerator<T> GetEnumerator()
    {
        for (int i = 0; i < Count; i++)
            yield return this[i];
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}
public static ArrayRow<T> GetRow<T>(this T[,] array, int index)
{
    return new ArrayRow<T>(array, index);
}

Alternatively you could copy the value of each row in the multi-dimensional array to a new single dimensional array, but then neither will reflect changes made to the other.

score 0 · Answer 3 · answered Apr 30 '15 at 13:51

For multidimensional arrays you need to access them like this:

// access 0,1
gameObjectData[0,1];

// access 5,4
gameObjectData[5,4];

// So in general is
gameObjectData[x,y];

You can't access it by just giving [x], so for your question it would be:

// asuming you want row 0
int row = 0;

// this give to g the size of the row of gameObjectData
int[] g = new int[gameObjectData.getLenght(row)];

for (int i = 0; i < gameObjectData.getLenght(row); i++)
{
   g[i] = gameObjectData[row,i];
}

score 0 · Answer 4 · answered Apr 30 '15 at 14:14

0

If you like one-liners, here is a LINQ one:

int rowIndex = 0;
firstRow = Enumerable.Range(0, gameObjectData.GetLength(1-rowIndex))
                     .Select(v => gameObjectData[rowIndex,v])
                     .ToArray();

answered Apr 30 '15 at 14:14

heltonbiker

26,657
28
137
252

Accessing one dimension of multidimensional array

4 Answers4