Adding a 2D array to the list. Found a bug and solution, need your explanation

[EARNEST]

Working fine:

        internal double[] AggregationMethod(List<double[]> listOf_D)
        {
            double[] maxD;
            double[] aggregatedD;
            List<double[]> tempList;

            maxD = new double[listOf_D[0].Length];
            
            tempList = new List<double[]>();

            for (int i = 0; i < maxD.Length; i++) 
            {

                aggregatedD = new double[listOf_D.Count]; 

                for (int j = 0; j < listOf_D.Count; j++) 
                {
                    aggregatedD[j] = listOf_D[j][i];
                }
                tempList.Add(aggregatedD);

                maxD[i] = aggregatedD.Max();
            }

            return maxD;
        }

Bug, while debugging, I see that after certain point, .ElementAt(0) starts changing while I'm trying to add new elements. What is the reason behind it?

        internal double[] AggregationMethod(List<double[]> listOf_D)
        {
            double[] maxD;
            double[] aggregatedD;
            List<double[]> tempList;

            maxD = new double[listOf_D[0].Length];
            
            tempList = new List<double[]>();

            aggregatedD = new double[listOf_D.Count]; 
            
            for (int i = 0; i < maxD.Length; i++) 
            {


                for (int j = 0; j < listOf_D.Count; j++) 
                {
                    aggregatedD[j] = listOf_D[j][i];
                }
                tempList.Add(aggregatedD);

                maxD[i] = aggregatedD.Max();
            }

            return maxD;
        }

Call by ref? or something like that? What are the ways to fix it, apart from re-initializing it?
Thanks in advance

[Rabbit]

I don't know C# but it seems that when you add the array to the list, it is not adding the values in the list, i.e. it is not instantiating a new array, copying the values, and then adding that new array to the list. Rather, it just adds the pointer to the array to the list. Therefore, unless you instantiate a new array, you are doing all your operations on the same array over and over.

You may not have to instantiate a new array each time if the list object had a method that allowed you to add a copy of the array. In which case, you are merely moving the instantiation out of your function into another function.