I get NullReferenceException error but I don't know why?

Question

I know that this error is shown where object is null. But in my case I'm not sure why is it shown. I tried to create 10 PictureBox objects on every 30px of width randomly, on timer_tick and here is my code.

PictureBox[] meteor;
int i=0;
Random rnd = new Random();

private void timer1_Tick(object sender, EventArgs e)
{
    if(i<10)
    { 
    int pozicija = rnd.Next(1, 25);
    pozicija *= 30;
    meteor[i] = new PictureBox()
    {
        Name = "pictureBox",
        BackColor = Color.Transparent,
        Size = new Size(80, 60),
        Location = new Point(pozicija, 0),
        Image = imageList2.Images[0],
    };
    this.Controls.Add(meteor[i]);
    }
    i++;
}

Error is pointed to this line of code

this.Controls.Add(meteor[i]);

Why Visual studio shows this error?

From that code, you should be getting a NullReferenceExeption earlier, at `meteor[i] = new PictureBox()`. — GSerg, Jun 02 '18 at 12:45
@SebastianHofmann I read that but i can find solution i said i know what it is. — Danilo Ivanovic, Jun 02 '18 at 12:51
In your case, you are not initializing `PictureBox[] meteor;`, it should be `PictureBox[] meteor = new PictureBox[1000];` (or any other range). — Sebastian Hofmann, Jun 02 '18 at 12:53
@SebastianHofmann That's what i was looking for thanks but no need for negative points — Danilo Ivanovic, Jun 02 '18 at 12:54
@DaniloIvanovic this is why the debugger is an essential tool. Always use that before asking anyone for help — maccettura, Jun 02 '18 at 12:56

score 1 · Accepted Answer · answered Jun 02 '18 at 13:08

1

You must instantiate the array first before using it, like this:

PictureBox[] meteor = new PictureBox[10];

Also I'm assuming that imageList2 has been defined and you have added an image to it.

answered Jun 02 '18 at 13:08

Islam El-gendy

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I get NullReferenceException error but I don't know why?

1 Answers1