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Practice Inheritance in C#

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Creating a Base Class

3:46 with James Churchill

In this video, we'll introduce our first challenge—creating a base class for our Media Library program media types.

Prerequisites

This practice session assumes that you've completed stage 3 of the C# Objects course. If you haven't done that yet, go check it out, then come back to this workshop.

This practice session also builds upon the skills that are covered in these two practice sessions that cover stages 1 and 2 of the C# Objects course.

If you haven't completed these practice sessions yet, you might consider doing that first before attempting this practice session.

Instructions

1st Challenge

  1. Add a MediaType base class to your program.

    • Add a public field named Title of type string.
    • Add a constructor to the MediaType class.
    • Define a parameter named title of type string.
    • Initialize the Title field using the title parameter.

  2. Update your existing media type classes to inherit from the MediaType base class.

    • Call the base class' constructor from each of the media type subclasses.

  3. Review your media type subclasses and remove any Title field definitions from those classes.

    • Remove any constructor initialization code related to the removed Title fields.

Help

If you get stuck on any of the following topics or simply need a refresher, click on a topic in list below to view the associated video in the C# Objects course.

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    [MUSIC] 0:00
    Hi There. This is James. 0:04
    In this C# practice session, you'll practice class inheritance using C#. 0:06
    It reinforces what you learned in stage three of the C# objects course. 0:12
    If you find this practice session too challenging to complete, 0:17
    you might need to review that course. 0:20
    See the teacher's notes for a link. 0:22
    This practice session is the third in a series of sessions 0:24
    where you'll build out a media library console application. 0:28
    Step-by-step you'll add features to the program. 0:31
    Eventually, you'll be able to use C# to add, list, and 0:35
    search for items like albums, books, and 0:39
    movies, whatever you want to have catalogued in your media library. 0:42
    In previous practice sessions, we defined the attributes and behaviors for 0:46
    our program's media type objects by adding class fields and methods. 0:51
    In this practice session, we'll see how we can use class inheritance to extend 0:56
    to all of our immediate type classes the behaviors 1:01
    that we currently have defined in just a single media type class. 1:04
    Go ahead and open your workspace from the previous practice session. 1:09
    Or you can open the workspace that I've attached to this video. 1:13
    If you want, you can download the project files in order to use an external editor 1:17
    or an IDE like Visual Studio. 1:22
    In the last practice session, we added behaviors to our album media type class. 1:25
    But really, these behaviors or 1:30
    methods should be available on all of our media types. 1:32
    We could copy and paste these methods to each of our other media type classes. 1:35
    This wouldn't be too much work given that we currently 1:40
    only have two other media type classes. 1:43
    But what if we had five or ten media type classes? 1:46
    Not only would this be a lot of extra work, in general, 1:50
    we should strive to avoid code duplication. 1:54
    Unnecessarily duplicating this code could make 1:57
    future maintenance on these classes more difficult to manage. 2:00
    So let's practice using object oriented programming 2:03
    in order to keep our code clean, concise, and easier to maintain. 2:06
    Remember from the C# objects course that classes define what it means to be 2:11
    in a particular classification. 2:16
    The album, book, and 2:18
    movie classes are all representations of their real life counterparts. 2:19
    They're also subclasses of a more generalized classification. 2:24
    Specifically, they're all media types. 2:28
    We need to create a media type base class. 2:32
    Then we can update our media type subclasses to inherit from the media 2:35
    type base class, allowing them to inherit the attributes and 2:40
    behaviors from the more generalized base class. 2:44
    For your first challenge, you'll add a MediaType base class to your program. 2:48
    Within that class, you'll define a public filed named Title of type string, 2:52
    and you'll add a constructor that defines a parameter named title, 2:57
    again of type string, that you'll use to initialize the Title field. 3:01
    After adding the base class, you'll update your existing media type classes to 3:06
    inherit from the MediaType base class. 3:10
    Then, from each of these media type subclasses, 3:13
    you'll call the base class's constructor. 3:16
    Lastly, you'll review your media type subclasses, and 3:19
    remove any title field definitions from those classes. 3:22
    You'll also remove from the constructors in those classes, 3:26
    any related field initialization code. 3:30
    And that's your first challenge. 3:33
    Don't worry if you aren't able to complete every part of this challenge. 3:35
    Complete as much of it as you can, and in the next video, I'll show you my solution. 3:38
    Good luck, and we'll see you in just a bit. 3:43

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