更改网格透明度

有这样的看法：

<Window x:Class="SampleMVVM.Views.MainView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:c="clr-namespace:SampleMVVM.Commands"
    Title="Main Window" Height="400" Width="350">

    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
        </Grid.ColumnDefinitions>

        <ListView ItemsSource="{Binding BooksList}" IsSynchronizedWithCurrentItem="True" Opacity="0.5">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <Border BorderBrush="Bisque" BorderThickness="1" Margin="10">
                        <StackPanel Margin="10">
                            <TextBlock Text="{Binding Title}" FontWeight="Bold"/>
                            <TextBlock Text="{Binding Author}" />
                            <StackPanel Orientation="Horizontal">
                                <TextBlock Text="Осталось:" />
                                <TextBlock Text="{Binding Count, Mode=TwoWay}" FontWeight="Bold" Margin="10,0"/>
                                <TextBlock Text="шт" />
                            </StackPanel>
                        </StackPanel>
                    </Border>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

        <ContentControl Grid.Column="1" Content="{Binding BooksList}">
            <ContentControl.ContentTemplate>
                <DataTemplate>
                    <Border BorderBrush="Bisque" BorderThickness="1" Margin="10">
                        <StackPanel Margin="10">
                            <TextBlock Text="Название:" />
                            <TextBox Text="{Binding Title, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,10"/>

                            <TextBlock Text="Автор:"/>
                            <TextBox Text="{Binding Author, UpdateSourceTrigger=PropertyChanged}" Margin="0,0,0,10"/>

                            <StackPanel Orientation="Horizontal">
                                <Button Content="Выдать" Command="{Binding GiveItemCommand}" Margin="10,0" />
                                <Button Content="Забрать" Command="{Binding GetItemCommand}" Margin="10,0" />
                            </StackPanel>
                        </StackPanel>
                    </Border>
                </DataTemplate>
            </ContentControl.ContentTemplate>
        </ContentControl>
    </Grid>
</Window>

如何在关注“ContentControl”时将“ListView”的透明度更改为 0.5？

更新。

附加问题：如何通过模型改变透明度？试图这样做。在模型中贴出代码：

private bool _isHidden;
public bool IsHidden
{
    get { return _isHidden; }
    set
    {
        _isHidden = value;
        OnPropertyChanged("IsHidden");
    }
}
public ICommand TestCommand
{
    get
    {
        return new DelegateCommand(new Action(() => {
            IsHidden = !_isHidden;
        }));
    }
}

在View中在ListView中添加了一个按钮和代码：

<ListView.Style>
        <Style TargetType="ListView">
            <Stye.Triggers>                    
                <!-- если у элемента с именем CC фокус внутри, -->
                <DataTrigger Binding="{Binding Path=IsHidden}" Value="True">
                        <!-- устанавливаем Opacity в 0.5 -->
                        <Setter Property="Opacity" Value="0.5"/>
                 </DataTrigger>
            </Style.Triggers>
         </Style>
</ListView.Style>

通过单击按钮，在代码中我看到 IsHidden 发生了变化，但 ListView 没有变得透明。