Added plain TextBox to test the databinding on CodeTextBox.

Befunge/Editor/MainWindow.xaml.cs

@@ -1,8 +1,34 @@
-using System.Windows;
+using System.ComponentModel;
+using System.Runtime.CompilerServices;
+using System.Windows;
+using Befunge.Editor.Annotations;
 using Befunge.Editor.CharStyles;
 
 namespace Befunge.Editor
 {
+    public class TextContext : INotifyPropertyChanged
+    {
+        private string _text;
+
+        public string Text
+        {
+            get { return _text; }
+            set
+            {
+                _text = value;
+                OnPropertyChanged(nameof(Text));
+            }
+        }
+
+        public event PropertyChangedEventHandler PropertyChanged;
+
+        [NotifyPropertyChangedInvocator]
+        protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
+        {
+            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+        }
+    }
+
     public partial class MainWindow
     {
         public MainWindow()