MaskedTextBox: fixed bug that was introduced with new "typing while all text selected overwrites value" feature, where the Tab key would cause the text to be deleted when all text was selected.

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

@@ -340,7 +340,8 @@ 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
-            if (SelectionLength == Text.Length)
+            //but only if the user is not tabbing / shift tabbing
+            if (SelectionLength == Text.Length && (e.Key != Key.Tab && e.Key != Key.LeftShift && e.Key != Key.RightShift))
             {
                 if (provider.RemoveAt(position, endposition))
                     UpdateText(provider, position);