Object reference not set to an instance of an object

Question

I have a class Cell:

public class Cell
{
    public enum cellState
    {
        WATER,
        SCAN,
        SHIPUNIT,
        SHOT,
        HIT
    }

             


        

Answer 1

Arrays are initialised to be empty - the Null reference is because HomeArray[i,j] is null, not because HomeArray[i,j].currentCell is null.

UPDATE: If you have a statement where a couple of different things could be null, then I generally split that up into multiple lines to make it easier to tell what is null.

For example, in your case:

MessageBox.Show(HomeArray[i,j].currentCell.ToString());

Either HomeArray[i,j] or HomeArray[i,j].currentCell could potentially be null and trigger a NullReferenceException - there is no way to tell which it was from the exception. If you split that statement up however:

Cell cell = HomeArray[i,j].currentCell;
MessageBox.Show(cell.ToString());

In this case if HomeArray[i,j] is null then you get your NullReferenceException on the first, line whereas if cell is null you get it on the second line.