TokenizedTextBox: handling proper deletion of tokens using the Back and Delete keys.

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/TokenizedTextBox/Implementation/TokenizedTextBox.cs

@@ -99,10 +99,16 @@ namespace Microsoft.Windows.Controls
             base.OnApplyTemplate();
 
             if (_rtb != null)
-                _rtb.TextChanged -= OnTextChanged;
+            {
+                _rtb.TextChanged -= RichTextBox_TextChanged;
+                _rtb.PreviewKeyDown -= RichTextBox_PreviewKeyDown;
+            }
             _rtb = GetTemplateChild("PART_ContentHost") as System.Windows.Controls.RichTextBox;
             if (_rtb != null)
-                _rtb.TextChanged += OnTextChanged;
+            {
+                _rtb.TextChanged += RichTextBox_TextChanged;
+                _rtb.PreviewKeyDown += RichTextBox_PreviewKeyDown;
+            }
 
             InitializeTokensFromText();
         }
@@ -111,7 +117,7 @@ namespace Microsoft.Windows.Controls
 
         #region Event Handlers
 
-        private void OnTextChanged(object sender, TextChangedEventArgs e)
+        private void RichTextBox_TextChanged(object sender, TextChangedEventArgs e)
         {
             if (_surpressTextChangedEvent)
                 return;
@@ -124,6 +130,39 @@ namespace Microsoft.Windows.Controls
             }
         }
 
+        void RichTextBox_PreviewKeyDown(object sender, KeyEventArgs e)
+        {
+            InlineUIContainer container = null;
+
+            if (e.Key == Key.Back)
+            {
+                container = _rtb.CaretPosition.GetAdjacentElement(LogicalDirection.Backward) as InlineUIContainer;
+            }
+            else if (e.Key == Key.Delete)
+            {
+                //if the selected text is a blank space, I will assume that a token item is selected.
+                //if a token item is selected, we need to move the caret position to the left of the element so we can grab the InlineUIContainer
+                if (_rtb.Selection.Text == " ")
+                {
+                    TextPointer moveTo = _rtb.CaretPosition.GetNextInsertionPosition(LogicalDirection.Backward);
+                    _rtb.CaretPosition = moveTo;
+                }
+
+                //the cursor is to the left of a token item
+                container = _rtb.CaretPosition.GetAdjacentElement(LogicalDirection.Forward) as InlineUIContainer;
+            }
+
+            //if the container is not null that means we have something to delete
+            if (container != null)
+            {
+                var token = (container as InlineUIContainer).Child as TokenItem;
+                if (token != null)
+                {
+                    SetTextInternal(Text.Replace(token.TokenKey, ""));
+                }
+            }
+        }
+
         #endregion //Event Handlers
 
         #region Methods