example of indexer

public int? this[int index] // indexer
        {
            get
            {
                return dynamicArray[index];
            }
            set
            {
                if (index > dynamicArray.Length) {

                    int?[] temp = new int?[index + 1]; // create temp array


                    for (int i = 0; i < dynamicArray.Length; i++) {
                        temp[i] = dynamicArray[i]; // copying content of array to temp array
                    }

                    dynamicArray = temp; // creating new array with new size

                    temp = null;
                }
            }
        }