WPF 验证错误模板

<Window x:Class="BindingExam.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:BindingExam"
        Title="MainWindow" Height="413.027" Width="488.793" FontSize="16">
    <Window.Resources>
        <Style TargetType="{x:Type TextBox}">
            <Setter  Property="Validation.ErrorTemplate">
                <Setter.Value>
                    <ControlTemplate>
                        <DockPanel LastChildFill="True">
                            <TextBlock DockPanel.Dock="Right" Foreground="Red" FontSize="14" FontWeight="Bold"
                                       ToolTip="{Binding ElementName=PlaceHolder,Path=AdornedElement.(Validation.Errors)[0].ErrorContent}">*</TextBlock>
                            <Border BorderBrush="Green" BorderThickness="1">
                                <AdornedElementPlaceholder Name="PlaceHolder"></AdornedElementPlaceholder>
                            </Border>
                        </DockPanel>
                    </ControlTemplate>
                    
                </Setter.Value>
            </Setter>
            <Style.Triggers>
                <Trigger Property="Validation.HasError" Value="true">
                    <Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self},Path=(Validation.Errors)[0].ErrorContent}">
                        
                    </Setter>
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
            <RowDefinition  Height="2*"></RowDefinition>
        </Grid.RowDefinitions>
        <ListBox Margin="3" Name="lstProducts" DisplayMemberPath="ModelName" VirtualizingPanel.CacheLength="3"></ListBox>
        <StackPanel Margin="3" Grid.Row="1" Orientation="Horizontal">
            <Button Margin="3" Grid.Row="1" Name="btnGetProducts" Click="btnGetProducts_Click_1">GetProducts</Button>
            <Button Margin="3" Grid.Row="1" Name="btnDelete" Click="btnDelete_Click_1">Delete</Button>
            <Label VerticalAlignment="Center">UnitCost></Label>
            <TextBox Width="200" Name="txtMinUnitCost">0</TextBox>
        </StackPanel>
        
        <Grid Grid.Row="2" Name="gridProduct" DataContext="{Binding ElementName=lstProducts, Path=SelectedItem}" Margin="8">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"></RowDefinition>
                <RowDefinition Height="Auto"></RowDefinition>
                <RowDefinition Height="Auto"></RowDefinition>
                <RowDefinition Height="Auto"></RowDefinition>
                <RowDefinition Height="*"></RowDefinition>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto"></ColumnDefinition>
                <ColumnDefinition Width="*"></ColumnDefinition>
               
            </Grid.ColumnDefinitions>
            <Label Margin="3">Model Number:</Label> 
            <TextBox Name="txtModelNumber" Margin="3" Grid.Column="1" Text="{Binding Path=ModelNumber, Mode=OneWay}" Grid.ColumnSpan="2"></TextBox>
            <Label Margin="3" Grid.Row="1">Model Name:</Label>
            <TextBox Name="txtModelName" Margin="3" Grid.Column="1" Grid.Row="1" Text="{Binding Path=ModelName, Mode=OneWay}" Grid.ColumnSpan="2"></TextBox>
            <Label Margin="3" Grid.Row="2">Unit Cost:</Label>
            <TextBox Name="txtUnitCost" Margin="3" Grid.Column="1" Grid.Row="2" Grid.ColumnSpan="2" Validation.Error="txtUnitCost_Error_1">
                <TextBox.Text>
                    <Binding Path="UnitCost" NotifyOnValidationError="True">
                        <Binding.ValidationRules>
                            <!--<ExceptionValidationRule></ExceptionValidationRule>-->
                            <!--<DataErrorValidationRule></DataErrorValidationRule>-->
                            <local:PositivePriceRule Min="0" Max="1000"></local:PositivePriceRule>
                        </Binding.ValidationRules>
                    </Binding>
                </TextBox.Text>
            </TextBox>
            <Label Margin="3" Grid.Row="3">Description:</Label>
            <TextBox Name="txtDescription" Margin="3" Grid.Column="0" Grid.Row="4" Grid.ColumnSpan="3" Text="{Binding Path=Description, Mode=OneWay}"
                     TextWrapping="Wrap"></TextBox>
        </Grid>
    </Grid>
</Window>