<Window x:Class="ClassicControls.TextBoxTest" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="TextBoxTest" Height="325" Width="390"> <Grid Margin="5"> <Grid.RowDefinitions> <RowDefinition Height="2*"></RowDefinition> <RowDefinition Height="*"></RowDefinition> </Grid.RowDefinitions> <TextBox Name="txt" VerticalScrollBarVisibility="Auto" TextWrapping="Wrap" AcceptsReturn="True" SelectionChanged="txt_SelectionChanged" SpellCheck.IsEnabled="True">this is a test</TextBox> </Grid> </Window> //File:Window.xaml.cs using System; using System.Collections.Generic; using System.Text; using System.Windows; using System.Windows.Controls; using System.Windows.Data; using System.Windows.Documents; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Imaging; using System.Windows.Shapes; namespace ClassicControls { public partial class TextBoxTest : System.Windows.Window { public TextBoxTest() { InitializeComponent(); } private void txt_SelectionChanged(object sender, RoutedEventArgs e) { Console.WriteLine(txt.SelectionStart); Console.WriteLine(txt.SelectionLength); Console.WriteLine(txt.SelectedText); } } }