需要修改TextBox的控件模板.向样式添加触发器是不够的.这应该有效:

You need to modify the control template of the TextBox. Adding a trigger to the style is not enough. This should work:

<Style TargetType="TextBox">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TextBox}">
                <Border x:Name="border" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
                    <ScrollViewer x:Name="PART_ContentHost" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden"/>
                </Border>
                <ControlTemplate.Triggers>
                    <Trigger Property="IsEnabled" Value="false">
                        <Setter Property="Opacity" TargetName="border" Value="0.56"/>
                    </Trigger>
                    <Trigger Property="IsMouseOver" Value="true">
                        <Setter Property="BorderBrush" TargetName="border" Value="#FF7EB4EA"/>
                    </Trigger>
                    <Trigger Property="IsFocused" Value="true">
                        <Setter Property="BorderBrush" TargetName="border" Value="Yellow"/>
                    </Trigger>
                </ControlTemplate.Triggers>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

您可以在 WPF 源代码中找到原始样式模板:https://github.com/dotnet/wpf/blob/c271205b80c27df976acbd7236ec637090d127c1/src/Microsoft.DotNet.Wpf/src/TextL.Box1X5AML-L441

You can find the original style template in the WPF source code: https://github.com/dotnet/wpf/blob/c271205b80c27df976acbd7236ec637090d127c1/src/Microsoft.DotNet.Wpf/src/Themes/XAML/TextBox.xaml#L415-L441