Border Class

原文链接：Border Class
Namespace:System.Windows.Controls
Assembly:PresentationFramework.dll

Draws a border, background, or both around another element.

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弹出框阴影效果：
XAML代码：

<Window x:Class="PopupDemo.MainWindow"        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"        Title="MainWindow" Height="350" Width="525">    <Grid Background="LightBlue">        <Grid Width="300" Height="300">            <Grid.RowDefinitions>                <RowDefinition Height="50"/>                <RowDefinition Height="50"/>                <RowDefinition Height="50"/>                <RowDefinition/>            </Grid.RowDefinitions>            <Button Content="注册" Grid.Row="2" Width="100" Height="23" HorizontalAlignment="Right" Click="Button_Click"></Button>        </Grid>        <Popup AllowsTransparency="True" Placement="Center" StaysOpen="False" x:Name="popup">            <Border Background="White" CornerRadius="20" Margin="20">                <Border.Effect>                    <DropShadowEffect BlurRadius="15" Direction="-90" RenderingBias="Quality" ShadowDepth="2"/>                </Border.Effect>                <Grid Width="300" Height="300">                    <Button Content="弹窗测试" Grid.Row="2" Width="100" Height="23"></Button>                 </Grid>            </Border>        </Popup>    </Grid>    </Window>

效果图：

备注：

必须有这两个才能显示出该效果。