How to make a part of the TextBox ReadOnly in WPF

The following post contains example how to make a part of textbox readonly.

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<Window x:Class="PartialReadOnlyTextBox.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Icon="Resources/Images/favicon-image.png" Title="Partial ReadOnly TextBox" Height="157" Width="536" ResizeMode="NoResize" ShowActivated="True" WindowStartupLocation="CenterScreen" Loaded="Window_Loaded"> <Grid> <TextBox Name="txtControl" VerticalAlignment="Center" ContextMenu="{x:Null}" PreviewKeyDown="txtControl_PreviewKeyDown"/> </Grid> </Window>

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using System; using System.Windows; using System.Windows.Input; namespace PartialReadOnlyTextBox { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { /// <summary> /// Get the original text. /// </summary> internal String OriginalText { get; private set; } public MainWindow() { InitializeComponent(); } /// <summary> /// Handels the Loaded event of Window. /// </summary> /// <param name="sender"></param> /// <param name="e"></param> /// <Developer>Kaushik Kumar Mistry</Developer> /// <DateCreated>25 Sep, 2013</DateCreated> /// <ModifiedBy>...</ModifiedBy> /// <ModifiedDate>...</ModifiedDate> /// <ModificationLog>...</ModificationLog> private void Window_Loaded(object sender, RoutedEventArgs e) { try { this.txtControl.Text = this.OriginalText = "Hello softwareKaffee."; } catch (Exception ex) { MessageBox.Show(ex.ToString()); } } /// <summary> /// Handels the PreviewKeyDown event of txtControl. /// </summary> /// <param name="sender"></param> /// <param name="e"></param> /// <Developer>Kaushik Kumar Mistry</Developer> /// <DateCreated>25 Sep, 2013</DateCreated> /// <ModifiedBy>...</ModifiedBy> /// <ModifiedDate>...</ModifiedDate> /// <ModificationLog>...</ModificationLog> private void txtControl_PreviewKeyDown(object sender, KeyEventArgs e) { try { if (this.txtControl.CaretIndex < this.OriginalText.Length) { e.Handled = true; } else if (e.Key == Key.Back && this.txtControl.CaretIndex == this.OriginalText.Length) { e.Handled = true; } } catch (Exception ex) { MessageBox.Show(ex.ToString()); } } } }