MaskedTextBox: fixed issue where arrows would clear selected text

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

@@ -341,7 +341,7 @@ namespace Microsoft.Windows.Controls
 
             //if all text is selected and the user begins to type, we want to delete all selected text and continue typing the new values
             //but only if the user is not tabbing / shift tabbing or copying/pasting
-            if (SelectionLength == Text.Length && (e.Key != Key.Tab && e.Key != Key.LeftShift && e.Key != Key.RightShift &&
+            if (SelectionLength == Text.Length && (e.Key != Key.Tab && e.Key != Key.LeftShift && e.Key != Key.RightShift && e.Key != Key.Left && e.Key != Key.Right && e.Key != Key.Up && e.Key != Key.Down &&
                                                    (Keyboard.Modifiers & ModifierKeys.Control) != ModifierKeys.Control))
             {
                 if (provider.RemoveAt(position, endposition))