How to create an array of lists through C# classes?

Question

Arrays

Good afternoon. As planned, I have an array (map), each cell can contain many values ​​\u200b\u200bwith which I will need to work. Decided to implement through classes.

class map
    {       
        public  Coordinates[,] Coor;
        //параметры карты
        public int n; 
        public int m;
        public   map(int n) { this.Coor = new Coordinates[n, n];
            this.n = n; this.m = n;
        }
        public map(int n, int m) { this.Coor = new Coordinates[n, m]; this.n = n; this.m = m; }
    }
class Coordinates
    {
        public   List<int> Type=new List<int>();
    }

map Map = new map(2);
Map.Coor[1,1].Type.Add(1);
Map.Coor[1,1].Type.Add(2);
Map.Coor[0, 0].Type.Add(2);
Console.WriteLine("count "+Map.Coor[1, 1].Type.Count);

I get the error "Object reference not set to an instance of an object." I tried many combinations, but I don't know how to fix it. who knows the solution?

Answer 1

You have created an empty array Coorfor the elements. But you don't have the elements themselves. It is necessary new Coordinatesto do on all array, each element. And learn how to debug your code.

Answer 2

How to look for the causes of such similar errors:

• Set a breakpoint on the line with the error
  
• We look at what is there with the values ​​​​of variables
  

In your case:

We see that all elements of Coor are null.