Foundations

1. Create a new project in VS, name it “Circle”.
2. In the Solution Explorer, right-click on “Circle”, then on “Add…” and select “Class”. Then, select “Class”, write “Circle.cs” as the name of the file, and click on “Add”.
3. You are now suppose to have two .cs files opened and displayed in the Solution Explorer: Program.cs and Circle.cs.
4. Declare one single instance variable in Circle.cs, of type double and named radius. Write a set and a get method for this instance variable.
5. In Program.cs, write statements that create a new Circle object and set its radius to 2.3. Display its radius at the screen using the method you defined previously.

Extending the Class

1. In C#, Math.PI is a double holding an approximation of π. In the Main method of Program.cs, write a statement that displays its value at the screen.
2. In the Circle.cs file, add two methods:
   1. A method that returns the circumference of the circle that calls it (i.e., 2π times the radius),
   2. A method that returns the area of the circle that calls it (i.e., π times the radius squared).
3. Test those two methods in your Main program, by displaying at the screen the area and the circumference of the object you created at the previous exercise.

Custom Constructors

1. Write a constructor that takes a double as argument, and set the value of the radius created to the value given as a parameter. Note that you can’t compile your program anymore. Why?
2. Edit the way you were creating the object in the Main method to make your program complilable again. Instead of the default constructor (that isn’t available anymore), use the constructor you just defined.

3. Add a custom “no-args” constructor to your class, using

   public Circle() { }

4. Edit your Main method so that two objects are created: one using the “no-args” constructor, one using the constructor that takes an argument.

Post-implementation Design

Draw the UML diagram for the class you just implemented. Make sure it matches perfectly your implementation.