'Object reference not set to an instance of an object' Error

Question

The code below is throwing an error at the beginning of the if statement. I believe it has something do with the character array, however I am not sure why that is. Any help would be much appreciated.

 public void display_bits(int count)
    {

        //bits that will be displayed

        string[] disp_bits = new string[1000]; 
        string[] disp_to_bits = new string[1000];

        int disp_count = 0;

        for (int i = 0; i <= count; i++)
        {
            char[] chars = { '~', '+', '*' };


            if (bits[i].IndexOfAny(chars) != 0)
            {

                bits[i] = disp_bits[disp_count];
                to_bits[i] = disp_to_bits[disp_count];
                disp_count++;

            }         
        }
    }

For future reference, you may wan tot think about the difference between a compiler error and a runtime exception. — H H, Jan 22 '17 at 17:51

Matthew Cawley · Answer 1 · 2017-01-22T17:29:04.067

0

The bits string array doesn't appear to be initialized.

and

for (int i = 0; i <= count; i++)

might need changing to

for (int i = 0; i < count; i++)

So that your i index doesn't go outside the bounds of your array.

edited Jan 22 '17 at 17:29

answered Jan 22 '17 at 17:19

Matthew Cawley

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I did that in the class. Its a global variable – Jimmy Jan 22 '17 at 17:20
And it's definitely initialized i.e using the `new` keyword? – Matthew Cawley Jan 22 '17 at 17:22
Yes, I initialized it in the begining of the class using the sytax below: string[] bits = new string[1000]; string[] to_bits = new string[1000]; – Jimmy Jan 22 '17 at 17:24
All of which was done in the beginning of the class I created – Jimmy Jan 22 '17 at 17:25
It could be that `for (int i = 0; i <= count; i++)` needs changing to `for (int i = 0; i < count; i++)` – Matthew Cawley Jan 22 '17 at 17:31
That seemed to fix the problem. Do you know why that is? – Jimmy Jan 22 '17 at 17:37
@Jimmy, you initialized only 218 elements? – Roman Jan 22 '17 at 17:39
@Roma So I initialized 1000, because I am going to use this software to parse various text files. I made the bits and to_bits string arrays in the beginning of the class, and passed in 218 because that was the length of the string array after parsing. – Jimmy Jan 22 '17 at 17:42
because `i` starts at 0, and you're using a raw `count` (that starts at 1) to terminate the loop. So if there are 1000 items and you say _"continue this loop whilst `i` is less than or equal to `1000`"_ it will loop 1001 times and on the 1001st iteration you won't have a string to operate against because the array doesn't hold that many. – Matthew Cawley Jan 22 '17 at 17:44
Ahh, I see. Thanks! – Jimmy Jan 22 '17 at 17:47
Most welcome. Don't forget to mark as answer if this was helpful. Thanks. – Matthew Cawley Jan 22 '17 at 17:50

'Object reference not set to an instance of an object' Error

1 Answers1