в 15:31, 26 мая 2010

2010-05-26T15:31:18Z

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2010-05-26T11:38:55Z

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==Casting Objects==

<source lang="csharp">
using System;
public class MotorVehicle {
public string model;
public MotorVehicle(string model) {
this.model = model;
}
public void Start() {
Console.WriteLine(model + " started");
}
}
public class Product : MotorVehicle {
public bool convertible;
public Product(string model, bool convertible) :
base(model) {
this.convertible = convertible;
}
}

public class Motorcycle : MotorVehicle {
public bool sidecar;
public Motorcycle(string model, bool sidecar) :
base(model) {
this.sidecar = sidecar;
}
public void PullWheelie() {
Console.WriteLine(model + " pulling a wheelie!");
}
}
class MainClass {
public static void Main() {
Product myProduct = new Product("MR2", true);
MotorVehicle myMotorVehicle = (MotorVehicle)myProduct;
Console.WriteLine("myMotorVehicle.model = " + myMotorVehicle.model);
myMotorVehicle.Start();
Motorcycle myMotorcycle = new Motorcycle("V-Rod", true);
MotorVehicle myMotorVehicle2 = (MotorVehicle)myMotorcycle;
Console.WriteLine("myMotorVehicle2.model =" + myMotorVehicle2.model);
myMotorVehicle2.Start();
Motorcycle myMotorcycle2 = (Motorcycle)myMotorVehicle2;
Console.WriteLine("myMotorcycle2.model = " + myMotorcycle2.model);
Console.WriteLine("myMotorcycle2.sidecar = " + myMotorcycle2.sidecar);
myMotorcycle2.Start();
myMotorcycle2.PullWheelie();
}
}
</source>

==Casting objects: downcast==

<source lang="csharp">
using System;

public class CPU {
public string model;

public CPU(string model) {
this.model = model;
}

public void Start() {
Console.WriteLine(model + " started");
}
}

public class Intel : CPU {
public bool convertible;

public Intel(string model, bool convertible) : base(model) {
this.convertible = convertible;
}
}

public class AMD : CPU {
public bool sidecar;

public AMD(string model, bool sidecar) : base(model) {
this.sidecar = sidecar;
}

public void PullWheelie() {
Console.WriteLine(model + " pulling a wheelie!");
}

}

class Test {
public static void Main() {
Intel myIntel = new Intel("MR2", true);

// create a AMD object
AMD myAMD = new AMD("V-Rod", true);

// cast myAMD to CPU (upcast)
CPU myCPU2 = (CPU) myAMD;

// cast myCPU2 to AMD (downcast)
AMD myAMD2 = (AMD) myCPU2;

// myMotorCycle2 has access to all members of the AMD class
Console.WriteLine("myAMD2.model = " + myAMD2.model);
Console.WriteLine("myAMD2.sidecar = " + myAMD2.sidecar);
myAMD2.Start();
myAMD2.PullWheelie();
}
}

</source>

==Casting objects: upcast==

<source lang="csharp">
using System;

public class CPU {
public string model;

public CPU(string model) {
this.model = model;
}

public void Start() {
Console.WriteLine(model + " started");
}
}

public class Intel : CPU {
public bool convertible;

public Intel(string model, bool convertible) : base(model) {
this.convertible = convertible;
}
}

public class AMD : CPU {
public bool sidecar;

public AMD(string model, bool sidecar) : base(model) {
this.sidecar = sidecar;
}

public void PullWheelie() {
Console.WriteLine(model + " pulling a wheelie!");
}

}

class Test {
public static void Main() {
Intel myIntel = new Intel("MR2", true);

// cast myIntel to CPU (upcast)
CPU myCPU = (CPU) myIntel;

Console.WriteLine("myCPU.model = " + myCPU.model);
myCPU.Start();
}
}

</source>

==Downcast will fail.==

<source lang="csharp">
class Employee { }

class ContractEmployee : Employee { }

class CastExample3
{
public static void Main ()
{
ContractEmployee ce = (ContractEmployee)new Employee();
}
}
</source>

==This code raises an exception at run time because of an invalid cast==

<source lang="csharp">
using System;

public class Starter {
public static void Main() {
MyClass obj = new MyClass();
// Fails at compile time
// YClass alias=obj;
// Fails at run time
YClass alias = (YClass)obj;
obj.MethodA();
obj.MethodB();
}
}
public class MyClass {
public virtual void MethodA() {
}
public virtual void MethodB() {
}
}
public class YClass : MyClass {
public override void MethodA() {
}
}
</source>

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в 15:31, 26 мая 2010

Admin: 1 версия