class Program { static void Main(string[] args) { Animal animal = new Dog(); animal.OverRideMe(); //animal.NewMethod(); Dog dog = (Dog)animal; dog.OverRideMe(); dog.NewMethod(); Console.Read(); } } public abstract class Animal { public Animal() { Console.WriteLine("Base Constructor"); } public virtual void OverRideMe() { Console.WriteLine("In Base Class's OverRideMe"); Console.Read(); } } public class Dog : Animal { public Dog() { Console.WriteLine("Derived Constructor"); } public override void OverRideMe() { Console.WriteLine("In Derived Class's OverRideMe"); Console.Read(); } public void NewMethod() { Console.WriteLine("In Derived Class's NewMethod"); Console.Read(); } } Dan Homola
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Regarding Inheritance C#
I am trying to understand how inheritance works in C#. I wrote the following code:
class Program { static void Main(string[] args) { Animal animal = new Dog(); animal.OverRideMe(); //animal.NewMethod(); Dog dog = (Dog)animal; dog.OverRideMe(); dog.NewMethod(); Console.Read(); } } public abstract class Animal { public Animal() { Console.WriteLine("Base Constructor"); } public virtual void OverRideMe() { Console.WriteLine("In Base Class's OverRideMe"); Console.Read(); } } public class Dog : Animal { public Dog() { Console.WriteLine("Derived Constructor"); } public override void OverRideMe() { Console.WriteLine("In Derived Class's OverRideMe"); Console.Read(); } public void NewMethod() { Console.WriteLine("In Derived Class's NewMethod"); Console.Read(); } } The CIL(Common Intermediate Language) code for the Main() looks like the following:
.method private hidebysig static void Main ( string[] args ) cil managed { // Method begins at RVA 0x2050 // Code size 42 (0x2a) .maxstack 1 .entrypoint .locals init ( [0] class ConsoleApplication1.Animal animal, [1] class ConsoleApplication1.Dog dog ) IL_0000: nop IL_0001: newobj instance void ConsoleApplication1.Dog::.ctor() IL_0006: stloc.0 IL_0007: ldloc.0 IL_0008: callvirt instance void ConsoleApplication1.Animal::OverRideMe() IL_000d: nop IL_000e: ldloc.0 IL_000f: castclass ConsoleApplication1.Dog IL_0014: stloc.1 IL_0015: ldloc.1 IL_0016: callvirt instance void ConsoleApplication1.Animal::OverRideMe() IL_001b: nop IL_001c: ldloc.1 IL_001d: callvirt instance void ConsoleApplication1.Dog::NewMethod() IL_0022: nop IL_0023: call int32 [mscorlib]System.Console::Read() IL_0028: pop IL_0029: ret } // end of method Program::Main The lines in CIL that are troubling me are:
IL_000f: castclass ConsoleApplication1.Dog IL_0014: stloc.1 IL_0015: ldloc.1 IL_0016: callvirt instance void ConsoleApplication1.Animal::OverRideMe() IL_001b: nop IL_001c: ldloc.1 IL_001d: callvirt instance void ConsoleApplication1.Dog::NewMethod() After the castclass of animal to Dog type the code executes dog.OverRideMe();. This is translated to CIL as
IL_0016: callvirt instance void ConsoleApplication1.Animal::OverRideMe()
I had cast the animal object to Dog type. Why should dog.OverRideMe(); be translated to the above statement in CIL? The output of the above code is:
This output has nothing to do with Base class Animal but CIL still places a call to it.