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1.4 Constructors

In this exercise, you add three constructors with the following signatures (this is called overloading):
- An all-args constructor: Circle(double radius, double centerX, double centerY, string color)
- A default constructor: Circle()
- A constructor with only the radius: Circle(double radius)

Use the following default values: radius = 1, centerX = 0, centerY = 0, and color = "white".

TIP: You can easily add constructors by choosing CTRL+. and selecting Generate Constructor.... Select the attributes you want to use in the constructor and Visual Studio will do the rest.

  1. Add the following code to your Circle class: 

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    public Circle(double radius, double centerX, double centerY, string color)
{
    this.Radius = radius;
    this.CenterX = centerX;
    this.CenterY = centerY;
    this.Color = color;
}

public Circle(double radius)
{
    this.Radius = radius;
    this.CenterX = 0;
    this.CenterY = 0;
    this.Color = "white";
}

public Circle()
{
    this.Radius = 1;
    this.CenterX = 0;
    this.CenterY = 0;
    this.Color = "white";
}
    • A constructor has no return value.
    • The constructor always has exactly the same name as the class.
    • There can be multiple constructors, as long as they have different signatures (overloading).
    • In the all-args constructor, the names radius, centerX, centerY, and color appear twice. Once as an attribute of the Circle class and once as a parameter of the constructor. To avoid confusion, C# has the this keyword. This refers to the class itself. this.Radius therefore refers to the attribute of the class. The code this.Radius = radius assigns the value passed as a parameter to the attribute.

  2. Modify the code in the Main method as follows: 

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    Circle myAllArgsCircle = new Circle(3, 1, 4, "green");
Console.WriteLine(myAllArgsCircle.CalculatePerimeter());
Console.WriteLine(myAllArgsCircle.CalculateArea());

Circle myDefaultCircle = new Circle();
Console.WriteLine(myDefaultCircle.CalculatePerimeter());
Console.WriteLine(myDefaultCircle.CalculateArea());

Circle myRadiusCircle = new Circle(6);
Console.WriteLine(myRadiusCircle.CalculatePerimeter());
Console.WriteLine(myRadiusCircle.CalculateArea());

  3. Run your program. Your output will look like this: 

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    18.84955592153876
28.274333882308138
6.283185307179586
3.141592653589793
37.69911184307752
113.09733552923255

  4. Try some other values and view the output.