XNA false index out of bounds exception?

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Alright guys firstly I'm working with XNA 4, secondly I'm using ArrayLists.

Now the problem is, I have no idea why these exceptions occur however they DO occur and apparently incorrectly.

Here's the code where it happens:

C#

if (bullets.Count - 1 >= i)
                        {
                            bullets.RemoveAt(i);
                            bulDirVal.RemoveAt(i);
                        }

As you can see I even added the if statement so it wouldn't execute those lines unless 'i' is indeed within the range of the ArrayList. When the exception is thrown, my 'i' value is always contained within the range, and I have no idea what is going on.

Is there anything I'm overlooking?

Posted 23-Apr-11 7:30am

Raztor0

Updated 23-Apr-11 7:37am

v3

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Ed Nutting 23-Apr-11 14:48pm

Are you sure 'i' is within the range of both 'bullets' and 'bulDirVal'? Your if statement should look something like: if(i < bullets.Count && i < bulDirVal.Count) ... (FYI using '< X.Count' is better than 'X.Count - 1 >= ' as it is both clearer and computationally more efficient, but that is another topic :P)

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Nish Nishant · Answer 1 · 2011-04-23T10:52:00

Solution 1

As Edman pointed out, you only check one collection, you also need to check the other one.

Another possibility is that you have multiple threads that may be accessing the same collection. If so, you need to add some thread-sync in there.

Posted 23-Apr-11 10:52am

Nish Nishant

Updated 23-Apr-11 10:53am

v2

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Raztor0 23-Apr-11 16:57pm

Both the ArrayLists are always the same size and get expanded/reduced at the same time as well, and oh yes multiple threads definately seems like it could be the problem here :o thanks a lot both of you :)