Virtual and
Overriding keyword are used for method overriding. Method overriding is concept
of Polymorphism. New keyword is used for method hiding.
Now we
check how to use this keyword in c# by example.
Example 1:-
namespace
ConsoleProg
{
class A
{
public void show()
{
Console.WriteLine("A");
}
}
class B : A
{
public void show()
{
Console.WriteLine("B");
}
}
class C : B
{
public void show()
{
Console.WriteLine("C");
}
}
class Program
{
static void Main()
{
A a = new A();
a.show(); // print-- A
B b = new B();
b.show(); // print-- B
C c = new C();
c.show(); //
print-- C
A a1 = new B();
a1.show(); //
print-- A
}
}
}
Note:- But it show some warning message.
1.)
'ConsoleProg.B.show()' hides inherited member 'ConsoleProg.A.show()'. Use the
new keyword if hiding was intended.
2.) ‘ConsoleProg.C.show()' hides inherited
member 'ConsoleProg.B.show()'. Use the new keyword if hiding was intended.
Solution of
the above warning is use either new keyword or overriding keyword in derived
class in method.
Virtual And Overriding
keyword (Method overriding):-
If you want
to be method overriding in the derived class, then the base class method must
have the virtual keyword otherwise it will throw an error.
Example 2:-
namespace
ConsoleProg
{
class A
{
public virtual void show()
{
Console.WriteLine("A");
}
}
class B : A
{
public override void show()
{
Console.WriteLine("B");
}
}
class C : B
{
public override void show()
{
Console.WriteLine("C");
}
}
class Program
{
static void Main()
{
A a = new A();
a.show(); // print-- A
B b = new B();
b.show(); // print-- B
C c = new C();
c.show(); //
print-- C
A a1 = new B();
a1.show(); //
print-- B
}
}
}
New Keyword (Method
hiding):
New keyword
is used for method hiding the base class method from derived class.
Example 3:-
namespace
ConsoleProg
{
class A
{
public void show()
{
Console.WriteLine("A");
}
}
class B : A
{
public new void show()
{
Console.WriteLine("B");
}
}
class Program
{
static void Main()
{
A a = new A();
a.show(); // print-- A
B b = new B();
b.show(); // print-- B
A a1 = new B();
a1.show(); //
print-- B
}
}
}
Method Overriding and
Hiding:-
Example 4:-
namespace ConsoleProg
{
class A
{
public void show()
{
Console.WriteLine("A");
}
}
class B : A
{
public new virtual void show()
{
Console.WriteLine("B");
}
}
class C : B
{
public override void show()
{
Console.WriteLine("C");
}
}
class Program
{
static void Main()
{
A a = new A();
a.show(); // print-- A
B b = new B();
b.show(); // print-- B
C c = new C();
c.show(); //
print-- C
A a1 = new B();
a1.show(); //
print-- A
B b2 = new C();
b2.show(); // print-- C
A a2 = new C();
a2.show();//
print-- A
}
}
}
Example 5:
namespace
ConsoleProg
{
class A
{
public virtual void show()
{
Console.WriteLine("A");
}
}
class B : A
{
public override void show()
{
Console.WriteLine("B");
}
}
class C : B
{
public override void show()
{
Console.WriteLine("C");
}
}
class Program
{
static void Main()
{
A a = new A();
a.show(); // print-- A
B b = new B();
b.show(); // print-- B
C c = new C();
c.show(); //
print-- C
A a1 = new B();
a1.show(); //
print-- A
B b2 = new C();
b2.show();//
print-- C
A a2 = new C();
a2.show();//
print-- C
}
}
}
Example 6:
namespace
ConsoleProg
{
class A
{
public virtual void show()
{
Console.WriteLine("A");
}
}
class B : A
{
public override void show()
{
Console.WriteLine("B");
}
}
class C : B
{
public new void show()
{
Console.WriteLine("C");
}
}
class Program
{
static void Main()
{
A a = new A();
a.show(); // print-- A
B b = new B();
b.show(); // print-- B
C c = new C();
c.show(); //
print-- C
A a1 = new B();
a1.show(); //
print-- A
B b2 = new C();
b2.show(); //
print-- B
A a2 = new C();
a2.show(); //
print-- B
}
}
}
Important Point:
Override:-
1.) Use this keyword polymorphism
implementation along with virtual.
2.) With same name and parameter as in
base class.
3.) It is call called as run time
polymorphism.
4.) Also called as late binding.
New :-
1.) It is used in polymorphism concept.
2.) With same name and different
parameters.
3.) Compile time bindig.
4.) Also called early binding.
