WPF气泡提示框的简单制作

<TextBox Name="account" GotFocus="account_GotFocus" LostFocus="account_LostFocus" Style="{StaticResource LabelTextBox}" xl:ControlAttachProperty.Label="用户名:" Foreground="Black" Margin="10,10,273,271" Width="Auto" />

<Popup Name="pop3" AllowsTransparency="True" StaysOpen="True" PopupAnimation="Fade" IsOpen="False" PlacementTarget="{Binding ElementName=account}" Placement="Right" >
 <Label Style="{StaticResource tipLable}">
 <StackPanel Orientation="Horizontal">
 <Label Content="请输入用户名"/>
 </StackPanel>
 </Label>
 </Popup>

<Style TargetType="Label" x:Key="tipLable">
 <Setter Property="Template">
 <Setter.Value>
 <ControlTemplate TargetType="{x:Type Label}">
 <Grid>
 <Border CornerRadius="4" BorderBrush="Black" BorderThickness="1" VerticalAlignment="Top" Margin="8.5,0,0,0" Background="Yellow" HorizontalAlignment="Left" Padding="5">
 <ContentPresenter />
 </Border>
 <Canvas Width="10" Height="10" HorizontalAlignment="Left" VerticalAlignment="Top" Margin="0,10,0,0" Background="Transparent">
 <Path Stroke="Black" StrokeThickness="0.5" Fill="Yellow">
 <Path.Data>
 <PathGeometry Figures="M 10,0 L 10,0,0,5 L 0,5,10,10"/>
 </Path.Data>
 </Path>
 </Canvas>
 </Grid>
 </ControlTemplate>
 </Setter.Value>
 </Setter>
 </Style>