<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="TextDecorationExample.Window1" Title="TextDecoration Example" Width="720" Height="400" Loaded="WindowLoaded"> <StackPanel> <TextBlock Name="underlineTextBlock" FontSize="24" Width="180" VerticalAlignment="Center">The lazy dog</TextBlock> </StackPanel> </Window> //File:Window.xaml.cs using System; using System.Windows; using System.Windows.Media; namespace TextDecorationExample { public partial class Window1 : Window { private void WindowLoaded(object sender, EventArgs e) { TextDecorationCollection myCollection = new TextDecorationCollection(); TextDecoration myUnderline = new TextDecoration(); myUnderline.Location = TextDecorationLocation.Underline; // Set the solid color brush. myUnderline.Pen = new Pen(Brushes.Red, 1); myUnderline.PenThicknessUnit = TextDecorationUnit.FontRecommended; // Set the underline decoration to the text block. myCollection.Add(myUnderline); underlineTextBlock.TextDecorations = myCollection; } } }