CheckedListBox throwing argument out of range when it shouldn't

Question

This is a .NET 3.5 Winforms project.

I'm having a weird error trying to programmatically check the checkboxes in checkboxlist.

for (int i = 0; i < 5; i++)
{
    cBListForming.Items.Add((i + 1).ToString());
    cBListForming.SetItemChecked(i, true);
}

So it adds 5 items, from 1 to 5, and then have the added checkboxes checked by default. Nothing surprising.

On the first iteration of the loop, everything works fine but on the second iteration (i == 1), SetItemChecked throws an exception.

System.ArgumentOutOfRange {"Index was out of range. Must be non-negative and less than the size of the collection.\r\nParameter name: index"}

I can see the first checkbox checked visually as well. The rest of them aren't because of the above exception.

This is pretty baffling. Just for testing purposes, I tried to add the items first, and programmatically check them later with a second loop, but still the same issue happens, even though the count of the checkbox is 5.

I tried using SetItemCheckState instead. Again, same issue.

I think I might've broken the CheckedListBox component itself, or some weird framework bug that I've encountered.

Any insights to what's going on here would be really appreciated.

Answer 1

This is pretty frustrating, but it actually did turn out to be a framework bug (Maybe Winforms Designer had a hiccup).

Removing and readding the checkedlistbox in the designer made it work. No other changes.

Answer 2

Try the following:

for (int i = 0; i < 5; i++)
{
    cBListForming.Items.Add((i + 1).ToString(), true);
}

Answer 3

I'm assuming "cBListForming" is a checkbox list.

Check the number of checkboxlist you have. This might be the cause of the problem.

cBListForming.Count();