在 WPF 如何改變 ListBox 已選擇項目的樣式？

關於這個問題我也搞了好久，以下是完整範例：

其實重點在於要改變 ListBoxItem 的 Template 屬性，然後指定 IsSelected 屬性為 True 時的樣式。

<Window x:Class="Project_DependencyProperty.MainWindow"

        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"

        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"

        xmlns:local="clr-namespace:Project_DependencyProperty"

        Title="MainWindow" Height="513" Width="526">

    <Window.Resources>

        <local:TaskCollection x:Key="Tasks"/>

        <DataTemplate DataType="{x:Type local:Task}">

            <Border BorderThickness="1" BorderBrush="Blue" Margin="2" Padding="2">

                <Grid>

                    <Grid.ColumnDefinitions>

                        <ColumnDefinition Width="80*"/>

                        <ColumnDefinition Width="5*"/>

                        <ColumnDefinition Width="15*"/>

                    </Grid.ColumnDefinitions>

                    <TextBlock Text="{Binding Name}" Grid.Column="0"/>

                    <TextBlock Text=":" Grid.Column="1"/>

                    <TextBlock Text="{Binding Type}" Grid.Column="2"/>

                </Grid>

            </Border>

        </DataTemplate>

        <Style TargetType="ListBoxItem" x:Key="SelectedItem">

            <Setter Property="Template">

                <Setter.Value>

                    <ControlTemplate TargetType="{x:Type ListBoxItem}">

                        <Border Background="Gray"

                            CornerRadius="8"

                            BorderThickness="3"

                            x:Name="LBI"

                            Margin="0" >

                            <ContentPresenter/>

                        </Border>

                        <ControlTemplate.Triggers>

                            <Trigger Property="IsSelected" Value="true">

                                <Setter TargetName="LBI" Property="Background">

                                    <Setter.Value>Yellow</Setter.Value>

                                </Setter>

                            </Trigger>

                        </ControlTemplate.Triggers>

                    </ControlTemplate>

                </Setter.Value>

            </Setter>

            <Setter Property="Background" Value="LightBlue"/>

            <Style.Triggers>

                <Trigger Property="IsSelected" Value="True">

                    <Setter Property="Background" Value="Blue"/>

                </Trigger>

            </Style.Triggers>

        </Style>

    </Window.Resources>

    <Grid>

        <ListBox HorizontalContentAlignment="Stretch" Margin="17,18,10,13"

                 Name="listBox1" FontWeight="Normal" FontStyle="Normal"

                 ItemContainerStyle="{DynamicResource SelectedItem}"

                 SelectionMode="Extended">

            <ListBox.ItemsSource>

                <Binding Source="{StaticResource Tasks}"/>

            </ListBox.ItemsSource>

        </ListBox>

        <Grid.LayoutTransform>

            <ScaleTransform ScaleX="1.5" ScaleY="1.5"/>

        </Grid.LayoutTransform>

    </Grid>

</Window>