NullReferenceException adding to list within array

Question

Ok, im trying to make something but it isnt working out for me as well as i thought it would. Bassicly im trying to Add to a list within an custom class array, is this makes any sense. Here is some code to perhaps make it easier to understand:

public class pfft
{
    public class Player
    {
        public string Name { get; set; }
        public int br { get; set; }
    }
    public class team
    {
        public int totalbr { get; set; }
        public List<Player> players { get; set; }
    }
}
public pfft.team[] Teams;
public int tmcount = 4;
private void btn_team_Click(object sender, EventArgs e)
{
    Teams = new pfft.team[tmcount]();
    foreach(pfft.Player p in getallplayers())
    {
        Teams[0].players.Add(p);
    }
}

This is bassicly all im doing, but when trying to add the player to the players list it crashes. Object reference not set to an instance of an object. The p it is trying to add does contain values, I checked that in the debugger I have also tried calling

Teams[0].players = new List<pfft.Player>();

but when i try that it will give the Nullexception at that part...

You haven't initialized the array itself with any entries. You must assign a sized array to 'Teams' before addressing it with an index — Marvin Smit, Nov 30 '13 at 21:52
Almost all cases of `NullReferenceException` are the same. Please see "[What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net)" for some hints. — John Saunders, Nov 30 '13 at 21:52

Konrad Kokosa · Accepted Answer · 2013-11-30T22:16:19.573

1

You have two problems here:

Creation of array do not create its objects:

so you need to iterate through array and create those objects:
```
for (int i = 0; i < tmcount; ++i)
     Teams[i] = new pfft.team();
```

You are not initializing public List<Player> players { get; set; } after Teams = new pfft.team[tmcount]();:

Teams = new pfft.team[tmcount]();
foreach(pfft.Player p in getallplayers())
{
    Teams[0].players = new List<pfft.Player>();
    Teams[0].players.Add(p);
}

To not have to initialize players in each team, use a slightly different property:

public class Team
{
    private List<Player> players = new List<Player>();

    public int totalbr { get; set; }
    public List<Player> Players 
    {
        get { return players; }
        set { players = value; }
    }
}

edited Nov 30 '13 at 22:16

answered Nov 30 '13 at 21:51

Konrad Kokosa

16,563
2
36
58

I did try so.. when i do that i get this: http://puu.sh/5y6tg.png Or better: http://puu.sh/5y6z2.png, And im not sure what you mean with the first problem. – Kage Nov 30 '13 at 22:02
Ahhhhh i see.. i was looking in the right direction.. just didn't realise i needed to make a 'new team' beside the list of players. Thank you very much! – Kage Nov 30 '13 at 22:10
2

The initialization of `players` needs to occur before the `foreach` loop, not inside it. – Sam Harwell Nov 30 '13 at 22:13
It should but OP is using only Teams[0] here. – Konrad Kokosa Nov 30 '13 at 22:14
@280Z28 That is indeed what i was initially doing.. but while trying to figure out what was going wrong i changed a lot to try stuff out.. – Kage Nov 30 '13 at 22:24

NullReferenceException adding to list within array

1 Answers1