版权声明：我不生产代码，我只是代码的搬运工。 https://blog.csdn.net/qq_43307934/article/details/88962940

参考地址：https://blog.csdn.net/johnsuna/article/details/1895169

效果：

从上至下，分别为上划线（Overline)，中划线(StrikeThrough)，基线(Baseline)，下划线(Underline)。

1、 简单设置

<TextBlock TextDecorations="Strikethrough" Text="文字"/>

 C#后台设置：

textBlock1.TextDecorations = TextDecorations.Underline;

textBlock1为控件TextBlock的名称 

2、调整下划线与文字的距离

        <TextBlock FontSize="84"

                   Text="文字">

            <TextBlock.TextDecorations>

                <TextDecorationCollection>

                        <TextDecoration PenOffset="3" />

                    </TextDecorationCollection>

            </TextBlock.TextDecorations>

        </TextBlock>

3、为文字加双下划线

        <TextBlock FontSize="84"

                   Text="文字">

            <TextBlock.TextDecorations>

                <TextDecorationCollection>

                    <TextDecoration PenOffset="1" />

                    <TextDecoration PenOffset="3" />

                </TextDecorationCollection>

            </TextBlock.TextDecorations>

        </TextBlock>

4、下划线的颜色与厚度

        <TextBlock FontSize="84"

                   Text="文字">

            <TextBlock.TextDecorations>

                <TextDecoration PenOffset="10"

                                PenOffsetUnit="Pixel"

                                PenThicknessUnit="Pixel">

                    <TextDecoration.Pen>

                        <Pen Thickness="5"

                             Brush="Green" />

                    </TextDecoration.Pen>

                </TextDecoration>

            </TextBlock.TextDecorations>

        </TextBlock>

5、下划线的渐变色

        <TextBlock FontSize="84"

                   Text="文字">

            <TextBlock.TextDecorations>

                <TextDecoration PenOffset="10"

                                PenOffsetUnit="Pixel"

                                PenThicknessUnit="Pixel">

                    <TextDecoration.Pen>

                        <Pen Thickness="5">

                            <Pen.Brush>

                                <LinearGradientBrush Opacity="0.8"

                                                     StartPoint="0,0.5"

                                                     EndPoint="1,0.5">

                                    <LinearGradientBrush.GradientStops>

                                        <GradientStop Color="Yellow"

                                                      Offset="0" />

                                        <GradientStop Color="Red"

                                                      Offset="1" />

                                    </LinearGradientBrush.GradientStops>

                                </LinearGradientBrush>

                            </Pen.Brush>

                            <Pen.DashStyle>

                                <DashStyle Dashes="1,2,3" />

                            </Pen.DashStyle>

                        </Pen>

                    </TextDecoration.Pen>

                </TextDecoration>

            </TextBlock.TextDecorations>

        </TextBlock>

C#后台实现：（此部分作者：大可山人）

    TextDecoration myUnderline = new TextDecoration();

    Pen myPen = new Pen();

    myPen.Brush = new LinearGradientBrush(Colors.Yellow, Colors.Red, new Point(0, 0.5), new Point(1, 0.5));

    myPen.Brush.Opacity = 0.8;

    myPen.Thickness = 5;

    myPen.DashStyle = DashStyles.Dash;

    myUnderline.Pen = myPen;

    myUnderline.PenThicknessUnit = TextDecorationUnit.FontRecommended;

    TextDecorationCollection myCollection = new TextDecorationCollection();

    myCollection.Add(myUnderline);

    textBlockGood.TextDecorations = myCollection;