Array Initialization ways

Question

I know that we can initialise an array in one of two ways:

1. Loop (No Memory reflection issues)
2. Enumerable.Repeat (Probably causes memory issues? Link: Enumerable.Repeat has some memory issues?)

I have two questions:

1. Can we initialise an array using Array.ForEach in this manner?

   double[][] myarr = new double[13][];
   
   Array.ForEach(myarr, *enter_code_here*);
   

   I tried replacing enter_code_here with:

   s => s = new double[2];
   

   but it does not initialise myarr.

2. What are the other array initialisation methods without any memory issues?

Answer 1

You can use Enumerable.Repeat just fine to initialize any array. The only thing you need to be careful of is that if the array element is of a reference type there are two ways to go about it:

// #1: THIS ARRAY CONTAINS 10 REFERENCES TO THE SAME OBJECT
var myarr = Enumerable.Repeat(new object(), 10).ToArray();

// #2: THIS ARRAY CONTAINS REFERENCES TO 10 DIFFERENT OBJECTS
var myarr = Enumerable.Range(0, 10).Select(i => new object()).ToArray();

// #3: SAME RESULT AS #2 BUT WITH Enumerable.Repeat
var myarr = Enumerable.Repeat(0, 10).Select(i => new object()).ToArray();

Answer 2

A1: No, you can't. Foreach just executes method with element as parameter but don't modify elements.

A2: You can use the folowing method to resolve the issue

static T[][] CreateArray<T>(int rows, int cols)
{
    T[][] array = new T[rows][];
    for (int i = 0; i < array.GetLength(0); i++)
        array[i] = new T[cols];

    return array;
}