c# - Extension method does not fills an array

Question

I want to fill array of random numbers, but I want to do this with extension method and in result I have only 500 zeroes.

    public static IEnumerable<int> FillRandom(this IEnumerable<int> arr, int min, int max)
    {
        Random rndNum = new Random();

        foreach (var item in arr)
        {
            yield return rndNum.Next(min, max);
        }
    }


        int[] UndefinedNumbers = new int[500];
        UndefinedNumbers.FillRandom(1, 100); //Executing extension method.

Output

question from:https://stackoverflow.com/questions/65863768/extension-method-does-not-fills-an-array

Answer 1

Your extension method does not fill given array but return new enumerable.

var undefinedNumbers = new int[500];
var randomNumbers = undefinedNumbers.FillRandom(1, 100);

object.ReferenceEquals(undefinedNumbers, randomNumbers); // returns false

To fill given array change parameter type to

public static int[] FillRandom(this int[] array, int min, int max)
{
    Random rndNum = new Random();

    for(var i = 0; i < array.Length; i++)
    {
        array[i] = rndNum.Next(min, max);
    }
}

Usage

int[] randomNumbers = new int[500].FillRandom(1, 100);