Constructors and ToString

May 22, 2024 (01:30:57 PM)

This lab serves multiple goals:

Adding Constructors and ToString to An Existing Class

As a warm-up, you will practice writing constructors and ToString methods by adding them to a class you have already implemented and used.

A Constructor for Rectangle

  1. Open the “Rectangle” project you created in the “Rectangle Class” lab. You can use the “enriched” class that was shared previously if you prefer.
  2. In “Rectangle.cs”, add a constructor to Rectangle that takes two arguments, a length and a width, and uses them to initialize the length and width attributes.
  3. Within your Main method, you will notice that your new Rectangle() instantiation statements are now highlighted as errors. This is because Rectangle no longer has a zero-argument (or “no-args”) constructor. Change each instantiation statement to call your new two-arguments constructor. Use the initial length and width values that you previously used in SetLength() and SetWidth().
  4. Compile and execute your program and ensure your Rectangles still behave as expected.

A ToString Method

In the Main method of your program, you should have one or more statements that display the length and width of a Rectangle. For example, you may have used one when testing if your Swap method worked as intended; an example is shown below:

Console.WriteLine($"The rectangle's length is {myRectangle.GetLength()}" +
            $", its width is {myRectangle.GetWidth()}.");
Console.WriteLine($"The rectangle's length is {myRectangle.GetLength()}" +
            $", its width is {myRectangle.GetWidth()}.)";

We will add a ToString method to Rectangle to make it easier to display this information repeatedly.

  1. In “Rectangle.cs”, add the following method to the Rectangle class:

    public override string ToString()
        return $"Rectangle with length {length} and width {width}.\n";
  2. Within your Main method, find a WriteLine statement that displays the length and width of a Rectangle, and replace the calls to GetLength and GetWidth with a single call to ToString. For example, you can replace the statement

    Console.WriteLine($"The rectangle's length is {myRectangle.GetLength()}" +
            $", its width is {myRectangle.GetWidth()}.");


    Console.WriteLine($"My rectangle: {myRectangle.ToString()}");   
  3. Compile and execute your program. What do you observe about the new WriteLine statements?

A Room Class

Now, we will create a new Room class. You will be writing the attributes and methods, including a constructor and a ToString method.

Initial Set-Up

Create a Room class with three attributes. They will hold:

  1. the name of the room,
  2. the length of the room, and
  3. the width of the room.

Name the attributes the way you want and pick appropriate data types. We will want to be able to store the length and the width of rooms (expressed in meters) using floating point numbers.

Create six methods:

  • three methods to set the value of each attribute (“setters”)
  • three methods to get the value of each attribute (“getters”)

To test your Room class, you will need to edit your Main method. You will need to create a Room object. Set the three attributes by asking the user for the rectangle’s name, length, and width. Then display the name of the Room object on the screen.

Adding Methods

Now, add two methods:

  • A constructor that takes three arguments and uses them to initialize the length, width, and name of the room
  • A method that returns the area of the room in square meters

Test them before moving on.

A ToString Method

This final part will guide you in writing your own ToString method.

  1. To understand the need for such a method, start by trying to display an object “directly.” In your Main method, create a Room object called myKitchen and write:


    Compile and execute your program. Is the information displayed on the screen what you expected? Is it useful?

  2. Add the following to your Room class:

    public override string ToString()
          return "The name of the room is...";
  3. Test this method by adding the following to your Main method:

  4. Remove .ToString() from the previous statement and execute your program again. Did something change?

  5. “Expand” this method by having it return a more meaningful string. This string should also contain the name of the room and its dimensions in meters. Use format specifiers to make it look nice!

Pushing Further (Optional)

This last part is here to help you understand that the data stored in attributes is not necessarily the data displayed by the ToString method.

Internationalization of the Room Class

Suppose that we want to accommodate users who are more familiar with feet. Note that we do not want to change the meaning of our width and length attributes, which are still supposed to hold dimensions in meters, but we want to create methods that perform the conversions for us. Remembering that

  • 1 meter = 3.28084 feet,
  • 1 foot = 0.3048 meter,

add four methods to your class:

  • A method that returns the width of the room in feet,
  • A method that returns the length of the room in feet,
  • A method that returns the area of the room in square feet,

Then edit your ToString method to display the dimensions of the rooms in both meters and feet.