Listbox.ListIndex value

General
1

I always use this code to retrieve selected row from a listbox

  dim row as Integer = Listbox1.ListIndex
  If row < 0 Or row >= Listbox1.ListCount Then
    // Do Something
  End If

I know that Listbox1.ListIndex = -1 happen when there is no selected row. But, Is there any chances of Listbox1.ListIndex value will be higher or equal than Listbox1.ListCount?

2

No, but that doesn’t make the test any less valid. Defensive coding and all that.

3

I do not think so.
I can tell you that the number of lines in a listbox (listcount) is base 1
Listindex is base 0 and never is equal listcount :

if listbox1.listindex > -1 then 
// do Something
end if
4

I use Listbox1.SelCount > 0 instead.

It basically does the same thing as Listbox1.ListIndex > -1. It just offers me more flexibility. It kinda became my personal preference.

The SelCount value will be 1 of some row is selected. But obviously higher than 1 in case multiple rows are selected. In many cases, I have to display other types of data when multiple rows are selected.

And no, the ListIndex value will never be higher than the index number of the last row: ListCount - 1. (Minus one, because ListCount is 1 based, as Massimiliano mentioned)

5

Thank you all. That’s make me feel safe to remove Or row >= Listbox1.ListCount

6

The only place you might be able to find the value of row >= ListCount is in the CellBackgroundPaint event of a listbox. Since all cells will fire this event, there is a change that the row value of that event might be higher than ListCount-1