From Xojo Documentation

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

Supported for all project types and targets.

Indicates the type of selection allowed via mouse gestures.


Use the following class constants to set the selection type:

Value Class Constant Description
0 SelectionSingle Single row selection
1 SelectionMultiple Multiple row selection

The default is single-row selection. If multiple row selection is on, a ListBox will handle Edit ↠ Select All menu item commands by default as long as the Select All menu item is named EditSelectAll.