wpf新手 求解样式触发器问题

控件如下：

<StackPanel HorizontalAlignment="Right"  Orientation="Horizontal" MinWidth="100" >                    <!--添加按钮-->

                  <Button  Style="{StaticResource TitelButtonStyle}" >

                      <Grid>

                          <Image Source="添加.png" HorizontalAlignment="Left" RenderOptions.BitmapScalingMode="Fant" />

                          <TextBlock Margin="0,1,0,0" Foreground="White" Text="添加" HorizontalAlignment="Right" Width="28 "  />

                      </Grid>

                  </Button>

                  <Grid Width="1" Height="20" Background="White"  Opacity="0.5"  Margin="10,0,0,0"/>

                  <!--选项按钮-->

                  <Button  Style="{StaticResource TitelButtonStyle}" >

                      <Grid>

                          <Image Source="齿轮.png" HorizontalAlignment="Left" RenderOptions.BitmapScalingMode="Fant" />

                          <TextBlock Margin="0,1,0,0" Text="选项" HorizontalAlignment="Right" Width="28 "  />

                      </Grid>

                  </Button>

                  <Grid Width="1" Height="20" Background="White" Opacity="0.5"  Margin="10,0,0,0"/>

                  <!--关闭按钮-->

                  <Button Style="{StaticResource CloseButton}">

                      <Grid  Height="17"   Width="35">

                          <Image Source="关闭.png"  RenderOptions.BitmapScalingMode="Fant" />

                      </Grid>

                  </Button>

              </StackPanel>

样式如下：

<Style x:Key="CloseButton" TargetType="Button">

            <Setter Property="Opacity" Value="0.5"/>

            <Setter Property="Template">

                <Setter.Value>

                    <ControlTemplate TargetType="Button">

                        <Border Background="Transparent" BorderThickness="0" >

                            <ContentControl  Height="30"   Width="35" HorizontalAlignment="Center" VerticalAlignment="Center"  Content="{TemplateBinding Content}" Background="{TemplateBinding Background}"  />

                        </Border>

                    </ControlTemplate>

                </Setter.Value>

            </Setter>

            <Style.Triggers>

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

                    <Setter Property="Background" Value="#ff0000"/>

                    <Setter Property="Opacity" Value="1" />

                </Trigger>

            </Style.Triggers>

        </Style>

关闭按钮的应用的样式中，鼠标悬停触发器更改了两个属性，Opacity更改了可以生效，Background变更却没效果，求大神答疑