在wpf中扩展样式

我尝试了以下方法来扩展样式并在validationresult为true时添加工具提示消息。但它显示错误"属性样式设置多次"。如何为这种情况扩展样式?任何帮助都将不胜感激。谢谢。

<TextBox Width="500" Style="{StaticResource HasInvalidValue}">
                <TextBox.Text>
                    <Binding Path="Text" UpdateSourceTrigger="PropertyChanged">
                        <Binding.ValidationRules>
                            <Validator:PathFormatValidationRule/>
                        </Binding.ValidationRules>
                    </Binding>
                </TextBox.Text>
                <TextBox.Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource HasInvalidValue}">
                    <Style>
                        <Setter Property="ToolTip" Value="Enter Text."/>
                    </Style>
                </TextBox.Style>
            </TextBox>

样式定义为:

<Style x:Key="HasInvalidValue" TargetType="{x:Type TextBox}">
    <Style.Triggers>
        <Trigger Property="Validation.HasError" Value="true">
            <Setter Property="Background" Value="White"/>
            <Setter Property="ToolTip"
          Value="{Binding RelativeSource={x:Static RelativeSource.Self},
                          Path=(Validation.Errors)[0].ErrorContent}"/>
        </Trigger>
    </Style.Triggers>
</Style>

<TextBox Style="{StaticResource HasInvalidValue}" ...
...
</TextBox>

<TextBox.Style ...
</TextBox.Style>