I am not sure what your specific scenario is, but if you load the text box values as part of the page initialization, you should be able to create an instance of the class that can be used to hold the original data.
In your example, you don't show any getters/setters, binding, etc. Do you have more detailed code than shown above?
E.g., I will assume you have a class with the appropriate getters/setters.
You could do something along the lines of:
private Car originalCarValues;
void
Page_Loaded(object
sender, RoutedEventArgs
e)
{
...
originalCarValues = new Car();
originalCarValues.Light = Light;
originalCarValues.TailLight = TailLight;
originalCarValues.Seats = Seats;
originalCarValues.Gears= Gears;
}
Make sure that the text box values are loaded prior to initializing your originalCarValues instance.