MaskedTextBox: fixed IsEditable when pasting and deleting

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

@@ -207,7 +207,7 @@ namespace Microsoft.Windows.Controls
         void TextBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
         {
             //if the text is readonly do not add the text
-            if (TextBox.IsReadOnly)
+            if (!IsEditable)
             {
                 e.Handled = true;
                 return;
@@ -241,6 +241,9 @@ namespace Microsoft.Windows.Controls
 
         void TextBox_PreviewKeyDown(object sender, KeyEventArgs e)
         {
+            if (!IsEditable)
+                return;
+
             MaskedTextProvider provider = MaskProvider;
             int position = TextBox.SelectionStart;
             int selectionlength = TextBox.SelectionLength;
@@ -421,6 +424,9 @@ namespace Microsoft.Windows.Controls
 
         private void Paste(object sender, RoutedEventArgs e)
         {
+            if (!IsEditable)
+                return;
+
             MaskedTextProvider provider = MaskProvider;
             int position = TextBox.SelectionStart;