引入命名空间
xmlns:theme="clr-namespace:Microsoft.Windows.Themes;assembly=PresentationFramework.Aero2"
给控件添加引用，这个性能比较好。
例如给Combobox下拉框添加引用效果
<--! 其他代码-->
<Popup x:Name="PART_Popup" AllowsTransparency="true" Grid.ColumnSpan="2" IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}}" Placement="Bottom" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}">
<theme:SystemDropShadowChrome x:Name="shadow"
Color="Transparent"
RenderTransformOrigin ="5,5"
CornerRadius="4"
MinWidth="{Binding ActualWidth, ElementName=templateRoot}"
MaxHeight="{TemplateBinding MaxDropDownHeight}">
<--! Margin="10,10,0,0" 这个是重点，显示左边和上边的阴影,默认左下角就有阴影-->
<Border x:Name="dropDownBorder"
Margin="10,10,0,0"
CornerRadius="4"
Padding="10"
Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"
BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" >
<ScrollViewer x:Name="DropDownScrollViewer">
<Grid x:Name="grid" RenderOptions.ClearTypeHint="Enabled">
<Canvas x:Name="canvas" HorizontalAlignment="Left" Height="0" VerticalAlignment="Top" Width="0">
<Rectangle x:Name="opaqueRect" Fill="{Binding Background, ElementName=dropDownBorder}" Height="{Binding ActualHeight, ElementName=dropDownBorder}" Width="{Binding ActualWidth, ElementName=dropDownBorder}"/>
</Canvas>
<ItemsPresenter x:Name="ItemsPresenter" KeyboardNavigation.DirectionalNavigation="Contained" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Grid>
</ScrollViewer>
</Border>
</theme:SystemDropShadowChrome>
</Popup>
<--! 其他代码-->
效果如下：
阴影样式二
Margin="8,8,-2,-2" 这个是重点 控制阴影，显示左边和上边的阴影，调整左下角的阴影。
<--! 其他代码-->
<Popup x:Name="PART_Popup" AllowsTransparency="true" Grid.ColumnSpan="2" IsOpen="{Binding IsDropDownOpen, RelativeSource={RelativeSource TemplatedParent}}" Placement="Bottom" PopupAnimation="{DynamicResource {x:Static SystemParameters.ComboBoxPopupAnimationKey}}">
<theme:SystemDropShadowChrome x:Name="shadow"
Color="Transparent"
RenderTransformOrigin ="5,5"
CornerRadius="4"
MinWidth="{Binding ActualWidth, ElementName=templateRoot}"
MaxHeight="{TemplateBinding MaxDropDownHeight}">
<--! Margin="8,8,-2,-2" 这个是重点 控制阴影，显示左边和上边的阴影，调整左下角的阴影-->
<Border x:Name="dropDownBorder"
Margin="8,8,-2,-2"
CornerRadius="4"
Padding="10"
Background="{DynamicResource {x:Static SystemColors.WindowBrushKey}}"
BorderBrush="{DynamicResource {x:Static SystemColors.WindowFrameBrushKey}}" >
<ScrollViewer x:Name="DropDownScrollViewer">
<Grid x:Name="grid" RenderOptions.ClearTypeHint="Enabled">
<Canvas x:Name="canvas" HorizontalAlignment="Left" Height="0" VerticalAlignment="Top" Width="0">
<Rectangle x:Name="opaqueRect" Fill="{Binding Background, ElementName=dropDownBorder}" Height="{Binding ActualHeight, ElementName=dropDownBorder}" Width="{Binding ActualWidth, ElementName=dropDownBorder}"/>
</Canvas>
<ItemsPresenter x:Name="ItemsPresenter" KeyboardNavigation.DirectionalNavigation="Contained" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</Grid>
</ScrollViewer>
</Border>
</theme:SystemDropShadowChrome>
</Popup>
<--! 其他代码-->
标签：控件,效果,SystemDropShadowChrome,阴影,添加,引用 From： https://www.cnblogs.com/Peretsoft/p/18457022