For some reason if I have a listview that has checkboxes included it will not allow multiple selection using the shift key.
As far as I am aware I am using this correctly:
<ListView SelectionMode="Multiple" />
Please note I have removed all of the other settings in the code due to it being unneeded in this example.
I have also done Extended.
To use keyboard modifiers you need to set SelectionMode=”Extended” and then shift+click.
I cannot remember exactly but Multiple mode only works with Ctrl+Click on each item.
I have used that with listbox control, which is stripped down ListView anyway as far as I know.