NullReferenceException on trying to use my first user-defined type

Question

What I'm trying to do is define my own type that contains 2 ints to use in a 2-dimensional array. The application for this is using the array indexes as x,y coordinates for objects in 2-d space to be displayed. So object with data stored at array[13,5] would be displayed at x=13,y=5, and the properties of that object could be retrieved with array[13,5].property1, for example. The type I've defined is extremely simple:

chunkBlocks.cs:
public class chunkBlocks {
    public int blockType;
    public int isLoaded;
}

then, I initialize the array:

chunkBlocks[,] _bData = new chunkBlocks[17, 17];

This all compiles/runs without error. The NRE is thrown when I try to assign a value to one of the properties of the type. For debugging, I have the code written as:

_bData[i, n].blockType = 5;

and the NRE is thrown specifically on the .blockType portion. I've tried changing the type to initialize with 0 values for both ints to no avail:

public class chunkBlocks {
    public int blockType = 0;
    public int isLoaded = 0;
}

I've Googled around and searched SO, and I've not been able to turn up anything. I'm sure it's a relatively simple matter, but I'm not experienced enough to be able to pinpoint it.

Thanks!

Shaharyar · Accepted Answer · 2013-12-13 05:42:42Z

4

You need to initialize every instance of the array:

_bData[i, n] = new chunkBlocks();

Now assign the value to it:

_bData[i, n].blockType = 5;

You will have to initialize every instance, you just have declared them in the array.

answered Dec 13, 2013 at 5:42

Shaharyar

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Comments

Michael Petrotta · Accepted Answer · 2013-12-13 05:52:49Z

0

I think you should do this:

for(int i = 0;i<17;i++)
{
    for (int j = 0; j < 17; j++)
    {
         _bData[i, j] = new chunkBlocks ();
    }
}

edited Dec 13, 2013 at 5:52

Michael Petrotta

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answered Dec 13, 2013 at 5:46

Rajeev Ranjan

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