static void Main(string[] args)
{
#region Array of base class type created and intiialized with
// a member of each class in the hierarchy
ParentClass[] myArray = new ParentClass[3];
myArray[0] = new ParentClass();
myArray[1] = new ChildClass();
myArray[2] = new GrandChildClass();
// 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 the ParentMethod()
foreach (ParentClass element in myArray)
{
Console.Write("{0}: ", element.GetType());
element.ParentMethod();
}
Console.WriteLine();
#endregion
#region Demonstrate overriding a base class method by a child
// demonstrate a child method calling the parent's method
foreach (ParentClass element in myArray)
{
Console.Write("{0}: ", element.GetType());
element.ParentMethod();
}
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 (ParentClass element in myArray)
{
Console.Write("{0}: ", element.GetType());
element.Method2();
Console.WriteLine();
}
#endregion
#region Demonstrate use of "as" keyword
// repeat calls to SomeMethod
foreach (object element in myArray)
{
// casting and creating new variable using as
ParentClass pc = element as ParentClass;
// below is the explicit cast not using as
//ParentClass pc = (ParentClass)element;
Console.Write("{0}: ", pc.GetType());
pc.SomeMethod();
}
Console.WriteLine();
#endregion
#region Demonstrate use of "is" keyboard
Console.WriteLine("Demo use of is:");
foreach (ParentClass element in myArray)
{
if (element is GrandChildClass)
{
Console.WriteLine("GrandChild Class");
}
else if (element is ChildClass)
{
Console.WriteLine("Child Class");
}
else if (element is ParentClass)
{
Console.WriteLine("Parent Class");
}
}
Console.WriteLine();
#endregion
#region Switch with cases
Console.WriteLine("Demo Switch:");
foreach (ParentClass element in myArray)
{
switch (element)
{
case GrandChildClass gc:
Console.WriteLine("GrandChild in Switch");
break;
case ChildClass cc:
Console.WriteLine("Child Class in Switch");
break;
case ParentClass pc:
Console.WriteLine("Parent Class in Switch");
break;
default:
Console.WriteLine("default");
break;
}
}
Console.WriteLine();
#endregion
#region create object of "object" type but intialized of the
// base class type then cast it to the actual type so you can call
object obj = new ParentClass();
// cast ParentClass on obj to call parent method
((ParentClass)obj).ParentMethod();
// cast the grandchild class onto the parent class
ParentClass p2 = new GrandChildClass();
((GrandChildClass)p2).SpecializedMethod();
Console.WriteLine();
#endregion
}
static void Main(string[] args)
{
#region Array of base class type
// array of base class
ParentClass[] myArray = new ParentClass[3];
myArray[0] = new ParentClass();
myArray[1] = new ChildClass();
myArray[2] = new GrandChildClass();
// print array using a foreach
Console.WriteLine("Print ParentClass Array: ");
foreach (ParentClass entry in myArray)
{
Console.WriteLine("{0}: ", entry.GetType());
entry.ParentClassMethod();
}
Console.WriteLine();
#endregion
#region switch and foreach print
// foreach with switch, prints based on class type
Console.WriteLine("Foreach with switch: ");
foreach (ParentClass entry in myArray)
{
switch (entry)
{
case GrandChildClass x:
Console.WriteLine("GrandChildClass");
break;
case ChildClass b:
Console.WriteLine("ChildClass");
break;
case ParentClass c:
Console.WriteLine("ParentClass");
break;
default:
Console.WriteLine("Default.");
break;
}
}
Console.WriteLine();
#endregion
#region call parent method in a foreach loop through the array
// uses as keyword and calls parent class from child class
Console.WriteLine("Print foreach loop based on class:");
foreach (ParentClass entry in myArray)
{
ChildClass c1 = entry as ChildClass;
GrandChildClass g1 = entry as GrandChildClass;
ParentClass p1 = entry as ParentClass;
if (c1 == null)
{
Console.Write("{0} is not a child class: ",
entry.GetType());
entry.ParentClassMethod();
}
else
{
Console.Write("{0} is a child class that can call: ",
entry.GetType());
entry.ParentClassMethod();
}
}
Console.WriteLine();
#endregion
#region create object of parentclass demonstrate is
Console.WriteLine("Identify Child or Parent from myArray:");
foreach (object o in myArray)
{
// if-else with is: children print trap line, else gets types
if (o is ChildClass)
{
Console.Write("Child class: ");
Console.WriteLine(o.GetType());
}
else
{
Console.Write("Parent Class: ");
Console.WriteLine(o.GetType());
}
}
Console.WriteLine();
#endregion
#region creates new instances of classes
ParentClass pc = new ParentClass();
ChildClass cc = new ChildClass();
ParentClass pccc = new ChildClass();
// cast the grandchild class onto the parent class
ParentClass p2 = new GrandChildClass();
((GrandChildClass)p2).ParentClassMethod();
Console.WriteLine();
// calls the parent method using the child method
Console.WriteLine("Children calling the Parent Method:");
pc.ParentClassMethod();
cc.ParentClassMethod();
pccc.ParentClassMethod();
Console.WriteLine();
// array of objects, with object set to parent class
object[] AnotherArray = new object[3];
AnotherArray[0] = pc;
AnotherArray[1] = cc;
AnotherArray[2] = pccc;
Console.WriteLine("AnotherArray has pc {0}, cc {1}, and pccc {2}.",
AnotherArray);
Console.WriteLine();
#endregion
}