Items collection must be empty before using ItemsSource - Listbox
===

If I put a DataTrigger in a simple Listbox I get this runtime exception:

**Items collection must be empty before using ItemsSource**

My listbox without datatrigger (no exception):

    <ListBox ItemsSource="{Binding EdgedBoards}" SelectedItem="{Binding SelEdgedBoard, Mode=TwoWay}" DisplayMemberPath="Name">
             <ListBox.ItemContainerStyle>
                 <Style TargetType="{x:Type ListBoxItem}" BasedOn="{StaticResource {x:Type ListBoxItem}}">
                      <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
                 </Style>
             </ListBox.ItemContainerStyle>
    </ListBox>

My listbox with datatrigger:

    <ListBox ItemsSource="{Binding EdgedBoards}" SelectedItem="{Binding SelEdgedBoard, Mode=TwoWay}" DisplayMemberPath="Name">
                            <Style TargetType="{x:Type ListBox}" BasedOn="{StaticResource {x:Type ListBox}}">
                                <Setter Property="Focusable" Value="True" />
                                <Style.Triggers>
                                    <DataTrigger Binding="{Binding ElementName=EdgedBoardsAdd_UC, Path=Visibility}" Value="Visible">
                                        <Setter Property="Focusable" Value="False" />
                                    </DataTrigger>
                                </Style.Triggers>
                            </Style>
                            <ListBox.ItemContainerStyle>
                                <Style TargetType="{x:Type ListBoxItem}" BasedOn="{StaticResource {x:Type ListBoxItem}}">
                                    <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
                                </Style>
                            </ListBox.ItemContainerStyle>
                        </ListBox>

What's wrong with the latter code?