static void Main(string[] args)
{
// Using virtual keyword!
Base baseOb = new Base();
Derived1 dOb1 = new Derived1();
Derived2 dOb2 = new Derived2();
Base baseRef; // a base class reference
baseRef = baseOb;
baseRef.Who(); // This time, the method of the base class is executed.
baseRef.Who(2);
baseRef.Who();
Console.WriteLine("");
baseRef = dOb1;
baseRef.Who(); // Now, the method of the first derived class is executed.
baseRef.Who(2);
baseRef.Who();
Console.WriteLine("");
baseRef = dOb2;
baseRef.Who(); // Now, the method of the second derived class is executed.
baseRef.Who(2);
baseRef.Who();
// Using virtual in practice
/* Note that the shapes array is defined in the base class. The assigned elements are in the derived classes,
* hence they can only call on the method present in the base class!*/
TwoDShape[] shapes = new TwoDShape[5];
shapes[0] = new Triangle("right", 8.0, 12.0);
shapes[1] = new Rectangle(10);
shapes[2] = new Rectangle(10, 4);
shapes[3] = new Triangle(7.0);
shapes[4] = new TwoDShape(10, 20, "generic");
for (int i = 0; i < shapes.Length; i++)
{
//shapes[1].IsSquare(). You can see that we do not have access to this method here!
Console.WriteLine("object is " + shapes[i].name);
Console.WriteLine("Area is " + shapes[i].Area());
Console.WriteLine();
}
// Using abstract classes.
AbstractTwoDShape[] abstractshapes = new AbstractTwoDShape[4];
abstractshapes[0] = new TriangleFromAbstract("right", 8.0, 12.0);
abstractshapes[1] = new RectangleFromAbstract(10);
abstractshapes[2] = new RectangleFromAbstract(10, 4);
abstractshapes[3] = new TriangleFromAbstract(7.0);
for (int i = 0; i < abstractshapes.Length; i++)
{
Console.WriteLine("object is " + abstractshapes[i].name);
Console.WriteLine("Area is " + abstractshapes[i].Area()); // The same story again, meaning the last definition of Area for objects is grabbed!
Console.WriteLine();
}
// Object is the universal type, hence it can hold any class, though it is rarely used!
object obj = new object[] { 1, "1", 101d, abstractshapes[0], shapes[2] };
// Boxing and Unboxing
int x = 10;
Console.WriteLine(BoxAndUnBox.Sqrt(x)); // A boxing is performed here!
Console.ReadKey();
}
// Construct a copy of a TwoDShape object.
public TwoDShape(TwoDShape ob)
{
Width = ob.Width;
Height = ob.Height;
name = ob.name;
}