Csharp/CSharp Tutorial/Class/override
Содержание
- 1 new method: not override
- 2 Overridden Equals()
- 3 Override without "override" keyword
- 4 Overriding Virtual Methods
- 5 PrintValue() Added to the BaseClass Class
- 6 Resolving Ambiguity with the new Keyword
- 7 Resolving Ambiguity with the override Modifier
- 8 Three-level Override methods
- 9 Virtual and override member function
new method: not override
<source lang="csharp">using System; class BaseClass {
virtual public void Print()
{ Console.WriteLine("This is the base class."); }
} class DerivedClass : BaseClass {
override public void Print()
{ Console.WriteLine("This is the derived class."); }
} class SecondDerived : DerivedClass {
new public void Print()
{
Console.WriteLine("This is the second derived class.");
}
} class MainClass {
static void Main()
{
SecondDerived derived = new SecondDerived();
BaseClass mybc = (BaseClass)derived;
derived.Print();
mybc.Print();
}
}</source>
B.DoSomething A.DoSomething
Overridden Equals()
<source lang="csharp">using System; using System.Text;
class Person {
public Person(string fname, string lname, string ssn, byte a)
{
FirstName = fname;
LastName = lname;
SSN = ssn;
age = a;
}
public string FirstName;
public string LastName;
public string SSN;
public byte age;
public override bool Equals(object o)
{
Person temp = (Person)o;
if(temp.FirstName == this.FirstName &&
temp.LastName == this.LastName &&
temp.SSN == this.SSN &&
temp.age == this.age)
{
return true;
}
else
return false;
}
public override string ToString()
{
StringBuilder sb = new StringBuilder();
sb.AppendFormat("[FirstName= {0}", this.FirstName);
sb.AppendFormat(" LastName= {0}", this.LastName);
sb.AppendFormat(" SSN= {0}", this.SSN);
sb.AppendFormat(" Age= {0}]", this.age);
return sb.ToString();
}
public override int GetHashCode()
{
return SSN.GetHashCode();
}
}
class MainClass {
public static void Main(string[] args)
{
Person p1 = new Person("Fred", "Jones", "222-22-2222", 98);
Person p2 = new Person("Fred", "Jones", "222-22-2222", 98);
if(p1.Equals(p2) && p1.GetHashCode() == p2.GetHashCode())
Console.WriteLine("P1 and P2 have same state\n");
else
Console.WriteLine("P1 and P2 are DIFFERENT\n");
}
}</source>
P1 and P2 have same state
Override without "override" keyword
<source lang="csharp">using System; public class A {
public virtual void SomeMethod() {
Console.WriteLine( "A::SomeMethod" );
}
} public class B : A {
public void SomeMethod() {
Console.WriteLine( "B::SomeMethod" );
}
} public class MainClass {
static void Main() {
B b = new B();
A a = b;
a.SomeMethod();
}
}</source>
A::SomeMethod
Overriding Virtual Methods
<source lang="csharp">class Point2D {
public int X;
public int Y;
public virtual void PrintToConsole()
{
System.Console.WriteLine("({0}, {1})", X, Y);
}
}
class Point3D : Point2D {
public int Z;
public override void PrintToConsole()
{
System.Console.WriteLine("({0}, {1}, {2})", X, Y, Z);
}
}
class MyMainClass {
public static void Main()
{
Point2D My2DPoint = new Point2D();
Point3D My3DPoint = new Point3D();
My2DPoint.X = 100;
My2DPoint.Y = 200;
My3DPoint.X = 150;
My3DPoint.Y = 250;
My3DPoint.Z = 350;
My2DPoint.PrintToConsole();
My3DPoint.PrintToConsole();
}
}</source>
PrintValue() Added to the BaseClass Class
<source lang="csharp">using System;
public class BaseClass {
protected int Value;
public BaseClass()
{
Value = 123;
}
public virtual void PrintValue()
{
Console.WriteLine("Value: " + Value);
}
}
public class DerivedClass : BaseClass {
public void PrintValue()
{
Console.WriteLine("Value = " + Value);
}
}
class MainClass {
public static void Main()
{
DerivedClass DerivedClassObject = new DerivedClass();
DerivedClassObject.PrintValue();
}
}</source>
Resolving Ambiguity with the new Keyword
<source lang="csharp">using System;
public class BaseClass {
protected int Value;
public BaseClass()
{
Value = 123;
}
public void PrintValue()
{
Console.WriteLine("Value: " + Value);
}
}
public class DerivedClass : BaseClass {
new public void PrintValue()
{
Console.WriteLine("Value = " + Value);
}
}
class MainClass {
public static void Main()
{
DerivedClass DerivedClassObject = new DerivedClass();
DerivedClassObject.PrintValue();
}
}</source>
Resolving Ambiguity with the override Modifier
<source lang="csharp">using System;
public class BaseClass {
protected int Value;
public BaseClass()
{
Value = 123;
}
public virtual void PrintValue()
{
Console.WriteLine("Value: " + Value);
}
}
public class DerivedClass : BaseClass {
override public void PrintValue()
{
Console.WriteLine("Value = " + Value);
}
}
class MainClass {
public static void Main()
{
DerivedClass DerivedClassObject = new DerivedClass();
DerivedClassObject.PrintValue();
}
}</source>
Three-level Override methods
<source lang="csharp">using System; class BaseClass {
virtual public void Print(){
Console.WriteLine("This is the base class.");
}
} class DerivedClass : BaseClass {
override public void Print() {
Console.WriteLine("This is the derived class.");
}
} class SecondDerived : DerivedClass {
override public void Print()
{
Console.WriteLine("This is the second derived class.");
}
} class MainClass {
static void Main()
{
SecondDerived derived = new SecondDerived();
BaseClass mybc = (BaseClass)derived;
derived.Print();
mybc.Print();
}
}</source>
This is the second derived class. This is the second derived class.
Virtual and override member function
<source lang="csharp">class Class1
{
public virtual void Hello()
{
System.Console.Write( "Hello from Class1" );
}
}
class Class2 : Class1
{
public override void Hello()
{
base.Hello();
System.Console.Write( " and hello from Class2 too" );
}
public static void Main( string[] args )
{
Class2 c2 = new Class2();
c2.Hello();
}
}</source>
Hello from Class1 and hello from Class2 too
