关于WPF的圆角

失败案例

<Border CornerRadius="3" Width="100" Height="100">
      <StackPanel Background="Red"></StackPanel>
</Border>

换成下面就成功？为什么？

<Border CornerRadius="3" Background="Red" Width="100" Height="100">
    <StackPanel ></StackPanel>
</Border>

1设备Button圆角

<Button x:Name="but1" Content="软件介绍" HorizontalAlignment="Left" Margin="126,356,0,0" VerticalAlignment="Top" Width="128" Click="Button_Click" FontSize="20" Height="35" >
　　<Button.Template>
　　　　<ControlTemplate TargetType="{x:Type Button}">
　　　　　　<Border BorderBrush="{TemplateBinding Control.BorderBrush}" BorderThickness="1" CornerRadius="10">
　　　　　　　　<Border.Background>#FF8EB4D4</Border.Background>
　　　　　　　　<ContentPresenter Content="{TemplateBinding ContentControl.Content}" HorizontalAlignment="Center" VerticalAlignment="Center" />
　　　　　　</Border>
　　　　</ControlTemplate>
　　</Button.Template>
</Button>

2 设置TextBox圆角

<TextBox HorizontalAlignment="Left" Height="24" Margin="43,192,0,0" TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="98">
                <TextBox.Resources>
                    <Style TargetType="{x:Type Border}">
                        <Setter Property="CornerRadius" Value="8"/>
                        <Setter Property="BorderBrush" Value="#c1d0dc"/>
                    </Style>
                </TextBox.Resources>
</TextBox>

3PasswordBox设置圆角 

<PasswordBox x:Name="t2" HorizontalAlignment="Left" Margin="183,150,0,0" VerticalAlignment="Top" Width="114" Height="26" BorderBrush="{DynamicResource {x:Static SystemColors.ControlDarkBrushKey}}" FontSize="18" Password="&#xD;&#xA;">
                <PasswordBox.Resources>
                    <Style TargetType="PasswordBox">
                        <Setter Property="PasswordChar" Value="●"/>
                        <Setter Property="KeyboardNavigation.TabNavigation" Value="None"/>
                        <Setter Property="HorizontalContentAlignment" Value="Left"/>
                        <Setter Property="Padding" Value="1"/>
                        <Setter Property="FocusVisualStyle" Value="{x:Null}"/>
                        <Setter Property="AllowDrop" Value="true"/>
                        <Setter Property="Template">
                            <Setter.Value>
                                <ControlTemplate TargetType="PasswordBox">
                                    <Border CornerRadius="8" x:Name="Bd" Background="White" BorderBrush="#c1d0dc" BorderThickness="1" OpacityMask="{x:Null}">
                                        <ScrollViewer SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" x:Name="PART_ContentHost" Template="{DynamicResource ScrollViewerControlTemplate1}"/>
                                    </Border>
                                </ControlTemplate>
                            </Setter.Value>
                        </Setter>
                    </Style>
                </PasswordBox.Resources>
</PasswordBox>