From Xojo Documentation

Property (As Integer )
aListBox.SelectedRowIndex = newIntegerValue
IntegerValue = aListBox.SelectedRowIndex

New in 2019r2

Supported for all project types and targets.

The number of the selected row.


If no item is selected, SelectedRowIndex returns ListBox.NoSelection. If the ListBox is in multiple-row selection mode, then the number of the lowest selected row is returned. For example, if rows 1, 3, and 4 are selected, SelectedRowIndex returns 1.

You can put the ListBox into multiple-row selection mode by changing the RowSelectionType property.

Sample Code

The following code in the Change event handler displays the text in the first column of the selected row:

If Me.SelectedRowIndex >= 0 Then
MessageBox(Me.CellValueAt(Me.SelectedRowIndex, 0))
End If

The following code displays a message if no row is selected:

If ListBox1.SelectedRowIndex = ListBox.NoSelection Then
MessageBox("Please select a row first.")
End If