Chapter Review 
=========================

- Follow the lab assignment format to prepare this assignment. 
- Create a project folder called ``Ch10Classes`` to include the code for this 
  project.
- Question 6~10 require code and execution screenshots when applicable.  

#.  What is the keyword used to create an instance of a class? 

#. Can you create an object from a class resides in another file?

#.  What is the purpose of a constructor?
    
#.  Describe the process of implementing inheritance in polymorphism in steps. 

#.  If you want to use an instance variable (field) in a method, should you declare
    that instance variable in the method? Why?

#.  How do you create an instance of the following class?

    .. code-block:: 

        class DoMath
        {
            public int Sum(int num1, int num2)
            {
                var total = num1 + num2;
                return total;
            }
        }

#.  How do you use the following class to use the Sum method for summing up two integers? Prepare  
    your code in your Program.cs Main method. 
    
    .. code-block:: csharp

        static class SomeMath
        {
            public static int Sum(int a, int b)
            {
                return a + b;
            }
        }

#.  Define a ``Math`` class, when **instantiated**, offer the functionality of two 
    summing methods with the same name Sum that would take 2 and 3 arguments, 
    respectively, and sum them up and return the results. 

#. Change the preceding code to allow the passing of an unspecified number of integer arguments 
   (see, e.g., https://stackoverflow.com/questions/1996426/pass-multiple-optional-parameters-to-a-c-sharp-function). 
   Save the file in the project folder,call it SumManyArgs.cs and use SumManyArgs as the class name. 

#.  Does the following code define a public or private class? Add an access modifier without 
    changing the existing accessibility level. Show your changed code and explain why. 

    .. code-block:: 

        class Customer
        {
            // Fields, properties, methods and events go here...
        }

.. #.  What does the ``this`` keyword do in the context of this chapter?

.. #.  If we want users to be able to see the value of a private instance variable
..     from outside of the class, how do we do it?

.. #.  What is the general name of the category of public methods whose sole purpose
..     is to set a part of instance state to a new specified value?    

.. #.  If you do not explicitly assign a value to an instance variable in a
..     constructor, does the instance variable have a value?


.. #.  What is the general name of the category of methods that return
..     instance state values?
    
.. #.  Instance variables are usually visible from inside instance methods for
..     the class.  What is the exception?  In the exceptional case, what is
..     the workaround to allow access to the instance variable?
    
.. #.  Sometimes you need to refer explicitly to the current object.  How
..     do you do it?
 

.. #.  What is the return type for a setter method?
 


.. #.  If a class has one or more setter methods, is the object type 
..     immutable?
   
.. #.  Where in a class are instance variables declared?

.. #.  For most instance variables, what is the modifier used that does not
..     appear at the beginning of a local variable declaration?
   
.. #.  What is the lifetime of an instance variable:   
..     When does it come into existence, and how long does it last?
   
.. #.  Why do we generally make an instance variable ``private``?

.. #.  In what code can an instance variable be seen and used?

.. #.  Must instance variables and methods always be preceded by
..     an explicit object reference and ``.``?

.. #.  Can we refer to an instance variable in a part of the code 
..     where there is no current object?

.. #.  In what kind of method in a class definition are instance variables never
..     accessible?

.. #.  A method with what signature allows you to control how the string 
..     concatenation operate (``+``) generates a string from the object?
    
.. #.  If you write an override the ``ToString`` method in a class, should the method
..     print the string?   If not, what should it do with the resulting string?
    


.. #.  Can aliased objects cause problems when created for an immutable object? 
..     Mutable object?

.. #.  In a class with instance methods you can always design the class so variables
..     are instance variables and not local variables.  When should you
..     use local variables instead?
    
.. #. If an instance method has a formal parameter of the same type as the
..    class being defined,
..    can you refer to a private instance variable in the parameter object?  
..    May you change it?
..    How do you distinguish an instance variable for the current object from the
..    corresponding instance variable for the parameter object?