static void Main(string[] args)
{
#region An array of the base class type is created and initialized
// with a member of each class in the hierarchy
Parent[] myArray = new Parent[3];
myArray[0] = new Parent();
myArray[1] = new Child();
myArray[2] = new Grandchild();
#endregion
#region Show that a method belonging to the base class is called
// from a child instance
// create ParentMethod() in Parent and iterate through array
// calling this method to demonstrate that all child classes
// have access to it
foreach (Parent element in myArray)
{
Console.Write("{0}: ", element.GetType());
element.ParentMethod();
}
Console.WriteLine();
#endregion
#region Demonstrate overriding a base class method by a child
foreach (Parent element in myArray)
{
Console.Write("{0}: ", element.GetType());
element.SomeMethod();
}
Console.WriteLine();
#endregion
#region Demonstrate a child method calling the parent's method
// create a virtual method in parent
// override in child and call the parent as part of the implementation.
foreach (Parent element in myArray)
{
Console.Write("{0}: ", element.GetType());
element.Method2();
Console.WriteLine();
}
Console.WriteLine();
#endregion
#region Demonstrate use of "as" keyword
// repeat class to SomeMethod
foreach (object element in myArray)
{
//Parent p = element as Parent;
Parent p = (Parent)element;
Console.Write("{0}: ", p.GetType());
p.SomeMethod();
}
Console.WriteLine();
#endregion
#region Demonstrate use of "is" keyword
Console.WriteLine("Demo use of is");
foreach (Parent element in myArray)
{
// note: order is important
// Grandchild -> Child -> Parent = Grandchild -> Child -> Parent
// Parent -> Child -> Grandchild = Parent -> Parent -> Parent
if (element is Grandchild)
{
Console.WriteLine("Grandchild");
}
else if (element is Child)
{
Console.WriteLine("Child");
}
else if (element is Parent)
{
Console.WriteLine("Parent");
}
}
Console.WriteLine();
#endregion
#region switch
Console.WriteLine("Demo switch");
foreach (Parent element in myArray)
{
switch (element)
{
case Grandchild gc:
Console.WriteLine("Grandchild");
break;
case Child c:
Console.WriteLine("Child");
break;
case Parent p:
Console.WriteLine("Parent");
break;
default:
Console.WriteLine("default");
break;
}
}
Console.WriteLine();
#endregion
#region Create an object of "object" type, but initialized of the
// base class type, then cast it to the actual type so you can call
// a method
object obj = new Parent();
((Parent)obj).ParentMethod();
Parent p2 = new Grandchild();
((Grandchild)p2).SpecializedMethod();
#endregion
}