Csharp 我想在文本框悬停时在其底部显示一条线

TextBox是Control，因此可以像任何其他模板一样重新模板化.诀窍是确保有一个名为PART_ContentHost的子元素-通常是ScrollViewer-控件将使用它来呈现可编辑的文本.(有关详细信息，请参阅WPF Default Styles and Templates documentation for TextBox).

这里有一个简单的例子，它将在悬停时显示一条下划线，淡入/淡出0.25秒，并将占据TextBox‘S宽度的50%(这要归功于一些Grid列逻辑).你应该能够进一步调整它，以获得你想要的外观/行为.别忘了，你也可以在TextBox的子类中添加更多的DependencyProperty，以获得外观上的额外粒度.

<Style x:Key="ResponsiveTextBoxStyle"
       TargetType="TextBox"
       BasedOn="{StaticResource {x:Type TextBox}}">
    <Setter Property="BorderBrush"
            Value="Blue" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type TextBox}">
                <Grid>
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*" />
                        <RowDefinition Height="Auto" />
                    </Grid.RowDefinitions>
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                    <VisualStateManager.VisualStateGroups>
                        <VisualStateGroup x:Name="CommonStates">
                            <VisualState x:Name="Normal">
                                <Storyboard>
                                    <DoubleAnimation Storyboard.TargetName="Underline"
                                                     Storyboard.TargetProperty="(Border.Opacity)"
                                                     To="0"
                                                     Duration="0:00:00.25" />
                                </Storyboard>
                            </VisualState>
                            <VisualState x:Name="MouseOver">
                                <Storyboard>
                                    <DoubleAnimation Storyboard.TargetName="Underline"
                                                     Storyboard.TargetProperty="(Border.Opacity)"
                                                     To="1"
                                                     Duration="0:00:00.25" />
                                </Storyboard>
                            </VisualState>
                        </VisualStateGroup>
                    </VisualStateManager.VisualStateGroups>
                    <ScrollViewer Margin="0"
                                  Grid.Row="0"
                                  Grid.ColumnSpan="4"
                                  x:Name="PART_ContentHost" />
                    <Border x:Name="Underline"
                            Grid.Row="1"
                            Opacity="0"
                            BorderThickness="1"
                            Height="2"
                            Grid.Column="1"
                            Grid.ColumnSpan="2"
                            BorderBrush="{TemplateBinding BorderBrush}" />
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>