Save and load initial state of an array (int[,])

Question

I'm trying to save the state of an array so I can load it later in it's initial state. But I don't know how to make them separate instances, and not to reference each other. Here's some sample code:

static void Main(string[] args)
{
    int[,] first = new int[5, 5];
    int[,] second = first;

    for (int i = 0; i < 5; i++)
    {
        for (int j = 0; j < 5; j++)
        {
            first[i, j] = i * j;
        }
    }

    first[0, 0] = 10000;
    first = second;
    Console.WriteLine(first[0, 0]); //10000
}

So... you are wanting to allocate a *copy* of `first` and assign it to `second`? — crashmstr, Jul 16 '14 at 11:57
Yes, pretty much. I wan't to make some changes to first, and then revert them on restart command. — Martin Dzhonov, Jul 16 '14 at 12:05

score 2 · Accepted Answer · answered Jul 16 '14 at 12:07

int[,] second = first;

Means that the second array is a reference to first, they are the same object. You need to create a new array instance. You mention that you want to save the state of the array for later use and for this, you have to copy your original array like so:

int[,] first = new int[5, 5];
int[,] second = new int[5, 5];
Array.Copy(first, second, first.Length);

score 1 · Answer 2 · edited May 23 '17 at 11:50

1

If you want a separate instance, you need to instantiate it:

int[,] second = new int[5, 5];

Many ways of copying an array can be found here: Any faster way of copying arrays in C#?

edited May 23 '17 at 11:50

Community

1
1

answered Jul 16 '14 at 11:57

astef

8,575
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score 1 · Answer 3 · answered Jul 16 '14 at 12:01

1

first = second

Only copies the reference. You need to copy the elements one by one, just like the way you populate the first array.

answered Jul 16 '14 at 12:01

mtmk

6,176
27
32

score 1 · Answer 4 · answered Jul 16 '14 at 12:03

1

Create a shallow copy with Array.Clone()

answered Jul 16 '14 at 12:03

peterszabo

137
1
7

To use this you'll need a cast, e.g. `int[,] second = (int[,])first.Clone()`. – Olly Jul 16 '14 at 12:14

Save and load initial state of an array (int[,])

4 Answers4