Add max items to ListBox to avoid IndexOutOfRange

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i have to change file names serially, i change them with a stringbuilder array, put them in a "before" ListBox and in a "After" ListBox: while there are less than 19 items (height/itemHeight), everything works fine, if there isn't enough place, i get IndexOutOfRange exception

2.in the case i want to use try-catch, where do i have to put it?

I get the error in Program.cs at line Application.Run(new MainForm()); in Main() , do i have to catch exceptions here, or in the method Button_click, that add items to listBoxes?

i've seen that if you don't know what to do, you mustn't cacth exception, but i wanted to know a visual example (not the one in msdn.com, that uses console)

Thanks in advance

I get the error here:

C#

    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new MainForm());//error here
    }

here i work with listboxes
      
    for (int i = 0; i < songsnum; i++)
    {
        songListBef.Items.Add(Path.GetFileName(full_fname_ex[i]));
        fname_noex_b[i] = new StringBuilder(Path.GetFileNameWithoutExtension(full_fname_ex[i]));
        fname_noex_b[i].Remove(0, toRemove_bef);
        fname_noex_b[i].Remove(fname_noex_b[i].Length - toRemove_aft, toRemove_aft);
    }

...
    
    for (int i = 0; i < songsnum; i++)
    {
        fname_noex_b[i].Append(Path.GetExtension(full_fname_ex[i]));
        songListAft.Items.Add(fname_noex_b[i].ToString());
    }

Posted 3-Sep-13 2:20am

maxpesa

Updated 3-Sep-13 2:30am

Thanks7872

v4

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[no name] 3-Sep-13 8:29am

"do i have to catch exceptions here", no. Catch the exceptions where they are likely to be thrown and handle them there.

"a visual example", there is no visual example or a console example.

2 solutions

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Freak30 · Answer 1 · 2013-09-03T04:14:00

Solution 1

The ListBix is unlikely to be the source of the exception as you are only adding items. My guess is that the Arrays (or Lists or other containers) full_name_ex and fname_noex_b only contain 19 items.

I would suggest you go to Debug/Exceptions... in Visual Studio and set the Checkboxes to get the exceptions the moment they are thrown. This should help in getting the debugger to the exact loaction.

Posted 3-Sep-13 4:14am

Freak30

Comments

maxpesa 4-Sep-13 6:59am

for (int i = 0; i < songsnum ; i++)
{
fileListBef.Items.Add(Path.GetFileName(full_fname_ex[i]));
fname_noex_b[i] = new StringBuilder(Path.GetFileNameWithoutExtension(full_fname_ex[i]));
fname_noex_b[i].Remove(0, toRemove_bef); <---got exception here
fname_noex_b[i].Remove(fname_noex_b[i].Length - toRemove_aft,toRemove_aft);
}

idenizeni · Answer 2 · 2013-09-03T09:19:00

Solution 2

Not sure if this is your issue but it probably is; it looks like you are trying to add one more item to the ListBox than there is in your item list.

Let's say songsum = 20 and you loop from 0 to 20, that's actually 21 items. If you only have 20 items then you will get an IndexOutOfRange error.

Try this in your loops, notice we are checking for one less than the songsnum value...

C#

for (int i = 0; i < songsnum - 1; i++)
{
    songListBef.Items.Add(Path.GetFileName(full_fname_ex[i]));
    fname_noex_b[i] = new StringBuilder(Path.GetFileNameWithoutExtension(full_fname_ex[i]));  
    fname_noex_b[i].Remove(0, toRemove_bef);
    fname_noex_b[i].Remove(fname_noex_b[i].Length - toRemove_aft, toRemove_aft);
}

...

C#

for (int i = 0; i < songsnum - 1; i++)
{
    fname_noex_b[i].Append(Path.GetExtension(full_fname_ex[i]));
    songListAft.Items.Add(fname_noex_b[i].ToString());
}

Posted 3-Sep-13 9:19am

idenizeni

Comments

maxpesa 4-Sep-13 6:49am

but if i have, for example, 16 items, i don't get indexout, so the loop should be fine.
i got the same problem by the way

Freak30 4-Sep-13 8:54am

With your example code, you would only do 19 runs through the loop.

When you decrease songsnum and it works without exception, this means the arrays are not allocated with size songsnum but with a constant size.

idenizeni 4-Sep-13 12:59pm

Thanks, you are correct. In my hast I was thinking equal to or less.

maxpesa 5-Sep-13 9:41am

"decreasing", you intend "songsnum-1" or 16(or everything < 19) instead of 19?

Freak30 5-Sep-13 9:48am

The comment about "decreasing" was targeted at the original poster who wrote, that if he only uses 16 items (possibly by setting songsnum to 16 instead of 17, though he doesn't say that explicitely), he doesn't get an Exception.

maxpesa 5-Sep-13 10:29am

okokok
i finally solved: there was a 16 in StringBuilder[] fname_noex_b = new StringBuilder[16];

i used it at the beginning and now i forgot
sorry and thanks for your help