C# Passing and returning a multidimensional array

Question

I have a 2D array, that I fill randomly with numbers. The code I have for this works fine, however, to organise my code better I'm wanting to put the "fill it randomly with numbers" part into a method.

The array is created from the Main() method, as I plan on passing and returning the array to/from other methods that will manipulate it. I then tried to write the method for filling the array, but I'm unsure how to either pass a multidimensional array, or return one either. According to MSDN I need to use an "out" rather than a return.

This is what I've tried so far:

    static void Main(string[] args)
    {
            int rows = 30;
            int columns = 80;



            int[,] ProcArea = new int[rows, columns];

            RandomFill(ProcArea[], rows, columns);

    }

    public static void RandomFill(out int[,] array, int rows, int columns)
    {

        array = new int[rows, columns];


        Random rand = new Random();
        //Fill randomly
        for (int r = 0; r < rows; r++)
        {
            for (int c = 0; c < columns; c++)
            {
                if (rand.NextDouble() < 0.55)
                {
                array[r, c] = 1;
            }
            else
            {
                array[r, c] = 0;
            }
        }
    }

These are the errors I have:

"The best overloaded method match for 'ProcGen.Program.RandomFill(out int[*,*], int, int)' has some invalid arguments"
"Argument 1: cannot convert from 'int' to 'out int[*,*]'"

What am I doing wrong, and what can I do to fix these errors? Also, am I right in thinking, because I'm using "out" that all I need to do is:

RandomFill(ProcArea[], rows, columns);

instead of?:

ProcArea = RandomFill(ProcArea[], rows, columns);

Is there a proper way of calling the method?

Answer 1

There is no need of an out parameter in your code.

Arrays are passed by reference until, in the method, you initialise it with a new reference.

So, in your method, if you don't initialise it with a new reference, then you can go without using the out parameter and values will be reflected in the original array -

public static void RandomFill(int[,] array, int rows, int columns)
{

    array = new int[rows, columns]; // <--- Remove this line since this array
                                    // is already initialised prior of calling
                                    // this method.
    .........
}

Answer 2

Try:

RandomFill(out ProcArea, rows, columns);