TextBoxInputMaskBehavior work not well when IME opened

[zheng303525]

Hello, I run the last sample "ControlzEx.Showcase" in Windows 10, and when I input number in the textbox with IME("Chinese") opened, the caret index will set wrong position.
The reason is when open IME, the property TextBox.TextProperty will changed before TextInput event raise (if use default IME ,the TextInput event will raise before TextBox.TextProperty changed), so var position = this.GetNextCharacterPosition(AssociatedObject.CaretIndex); will get wrong caret index.
I'm sorry for that do not find any good way to fix it.