Assuming you meant 2018r4 and not 2014r4" as posted, the fact that it works fine under 2018r3 would seem to indicate a Xojo bug introduced in the last release. Of course, if you can't submit a sample project any feedback report will be closed as "not reproducible" :(

@Tim P How is the data being fetched?

The data is being fetched through a Xojo.Net.HTTPSocket and processed into the array in the PageReceived event handler before being sent to the listbox. Examination of the populated array immediately before the AddRow call shows that the data is there and correct, so I don't see how that could be the problem.

@Julian S Do you have any code inside the CellBackgroundPaint, CellTextPaint or DisclosureWidgetPaint events?
Is the ListBox sitting inside any other controls, or is it directly on the window?
What scale factor is your desktop?

There is no code in any of the cell-specific events. That was the first thing I removed in my debugging attempts. The listbox is directly on the window. The only other controls on the window are a pushbutton, a couple of labels, and a textfield, none of which encroach on the listbox. The scalefactor of the window is 1 (I don't think I've ever used this particular item).

@Julia T Assuming you meant 2018r4 and not 2014r4" as posted, the fact that it works fine under 2018r3 would seem to indicate a Xojo bug introduced in the last release. Of course, if you can't submit a sample project any feedback report will be closed as "not reproducible" :(

Oops! Yeah, that was a typo. I'm using 2018r4 when I see the problem, not 2014r4.

@Julian S s = Array ("1", "2", "3", "4", "5", "6", "7", "8")
listbox1.AddRow(s)

Yes. Only the 1, 2, and 3 show up.

Just for fun, I added a second listbox and added an AddRow call pointing to the second listbox immediately before the call to the original llistbox. This new listbox has no code in any event handler and, except for the column count, is totally vanilla.

Both listboxes show only the first three columns.

I need to do more detective work, I guess.

@Joseph E Maybe just loop through your array with a msgbox, examining the contents?

No, use the debugger to scan (read) what the array contents is.

Back to :

Dim num() As String = Array("1","2","3","4","5","6","7","8")
ListBox1.AddRow(num)

What happens if you use:

  Dim num() As String = Array("1","2","3","4","5","6","7","8")
  LB.AddRow(num)
  
  LB.ColumnCount = UBound(num)+1

Random thoughts:

The fact that your own test programs do not exhibit the problem may be a useful clue - look for differences between that case and your app that has the bug.

I assume that the problem only manifests when using AddRow and not if you write to the cells individually, right?

You said you tried listbox.invalidate - have you tried listbox.refresh?

@Emile S No, use the debugger to scan (read) what the array contents is.

Back to :

Dim num() As String = Array("1","2","3","4","5","6","7","8")
ListBox1.AddRow(num)

What happens if you use:
Dim num() As String = Array("1","2","3","4","5","6","7","8") LB.AddRow(num) LB.ColumnCount = UBound(num)+1

Checking the array in the debugger before and after the AddRow shows in both cases that the array contains the correct data. BTW, it's a String array so there's no on-the-fly conversions.

@Julia T Random thoughts:

The fact that your own test programs do not exhibit the problem may be a useful clue - look for differences between that case and your app that has the bug.

I assume that the problem only manifests when using AddRow and not if you write to the cells individually, right?

You said you tried listbox.invalidate - have you tried listbox.refresh?

Yes, I tried Listbox1.Refresh also and had the same results. As for writing to the cells individually, that caused only the first TWO cell to be displayed.

What is really confusing me about this is the fact that if I click on the listbox's Header, the cells in the listbox show all of the data in the cells. This tells me that the cells actually have the data in them but for some reason aren't displaying it.

My last statement in my post had me thinking. If it is just a display problem, maybe I should simply set the ListBox's Selected row to LastIndex and then remove the value. So I put in the code immediately after the AddRow

Listbox1.Selected(Listbox1.LastIndex) = True
Listbox1.Selected(Listbox1.LastIndex) = False

and that seems to work. It's about as ugly a solution workaround as there is but at least it works.

My thanks to everyone who gave suggestions and brain cells on this.

What's bugging me is that I have a vague recollection of encountering this myself at some time in the past, but my fading memory can't retrieve it, sorry :( I'll keep trying.

@Tim P Can you provide the project to someone to look at? Unfortunately, if the issue doesn't present itself in a demo project, there is nothing we can do here without seeing the project.

Don't feel bad about your workaround either, a similar style workaround is required to get the header to update if you're setting the listbox to unsorted and want the sort direction indicator to clear.

Thanks, Tim, but I don't have permission from the originator of the code to give it to anyone. Once the project is done, I plan to try to reproduce the issue in a demo project but so far haven't been able to.

No nap for me this afternoon, but when reading the answers in this Conversation, something comes back to my mind: a bug of mine…

Answer #1:
In a Listbox, I change the number of Columns at Insert time, then add some row(s), and a following addition (Paste) I noticed a miss in the number of columns. I added some columns and my data went back.

Answer #2:
If in your data (the data you want to Paste) you have an EndOfLine (Return, LF, Enter, whatever), you will not be able to watch anything but an empty line.
To check that, set your Listbox to all columns Editable(s) by a simple click (or a DoubleClick), and try to edit one of the “empty Cells”, place the cursor at the end of the Cell contents, then press the Delete key and watch carefully what happens…

Of coure, Tim is right: it is not easy to make diagnostics without seeing the project.

Back to the number of columns: when you change the number of columns of a Listbox, you do not delete the contents of the Listbox, you only display that amount of columns; if you change the number of colums back to the original number, you get your previous data back on display. (provided you do not delete the previous Rows / close the window, etc.

I was able to create a test app that shows the problem and created a FB report.

Feedback Case #54571