I have two classes:  

```
class Player
{
    public string Id { set; get; }
    public int yPos { set; get; }
    public List<Shot> shots;
    public Player(string _Id, int _yPos)
    {
        Id = _Id;
        yPos = _yPos;
    }

}
class Shot
{
    public int yPos { set; get; }
    public Shot(int _yPos)
    {
        yPos = _yPos;
    }
}

```

When I try to put new Shot in list of shots for the player I get NullReferenceException:  

```
Player pl = new Player("Nick",50);
pl.shots.Add(new Shot(pl.yPos)); // this line throws exception

```

Probably something ultimately simple.