Object.MemberwiseClone Método
Definición
protected:
System::Object ^ MemberwiseClone();
protected object MemberwiseClone ();
member this.MemberwiseClone : unit -> obj
Protected Function MemberwiseClone () As Object
Devoluciones
Copia superficial del Object actual.A shallow copy of the current Object.
Ejemplos
El ejemplo siguiente ilustra la MemberwiseClone método.The following example illustrates the MemberwiseClone method. Define un ShallowCopy
método que llama al MemberwiseClone método para realizar una operación de copia superficial en un Person
objeto.It defines a ShallowCopy
method that calls the MemberwiseClone method to perform a shallow copy operation on a Person
object. También define un DeepCopy
método que realiza una operación de copia en profundidad en un Person
objeto.It also defines a DeepCopy
method that performs a deep copy operation on a Person
object.
using System;
public class IdInfo
{
public int IdNumber;
public IdInfo(int IdNumber)
{
this.IdNumber = IdNumber;
}
}
public class Person
{
public int Age;
public string Name;
public IdInfo IdInfo;
public Person ShallowCopy()
{
return (Person) this.MemberwiseClone();
}
public Person DeepCopy()
{
Person other = (Person) this.MemberwiseClone();
other.IdInfo = new IdInfo(IdInfo.IdNumber);
other.Name = String.Copy(Name);
return other;
}
}
public class Example
{
public static void Main()
{
// Create an instance of Person and assign values to its fields.
Person p1 = new Person();
p1.Age = 42;
p1.Name = "Sam";
p1.IdInfo = new IdInfo(6565);
// Perform a shallow copy of p1 and assign it to p2.
Person p2 = p1.ShallowCopy();
// Display values of p1, p2
Console.WriteLine("Original values of p1 and p2:");
Console.WriteLine(" p1 instance values: ");
DisplayValues(p1);
Console.WriteLine(" p2 instance values:");
DisplayValues(p2);
// Change the value of p1 properties and display the values of p1 and p2.
p1.Age = 32;
p1.Name = "Frank";
p1.IdInfo.IdNumber = 7878;
Console.WriteLine("\nValues of p1 and p2 after changes to p1:");
Console.WriteLine(" p1 instance values: ");
DisplayValues(p1);
Console.WriteLine(" p2 instance values:");
DisplayValues(p2);
// Make a deep copy of p1 and assign it to p3.
Person p3 = p1.DeepCopy();
// Change the members of the p1 class to new values to show the deep copy.
p1.Name = "George";
p1.Age = 39;
p1.IdInfo.IdNumber = 8641;
Console.WriteLine("\nValues of p1 and p3 after changes to p1:");
Console.WriteLine(" p1 instance values: ");
DisplayValues(p1);
Console.WriteLine(" p3 instance values:");
DisplayValues(p3);
}
public static void DisplayValues(Person p)
{
Console.WriteLine(" Name: {0:s}, Age: {1:d}", p.Name, p.Age);
Console.WriteLine(" Value: {0:d}", p.IdInfo.IdNumber);
}
}
// The example displays the following output:
// Original values of p1 and p2:
// p1 instance values:
// Name: Sam, Age: 42
// Value: 6565
// p2 instance values:
// Name: Sam, Age: 42
// Value: 6565
//
// Values of p1 and p2 after changes to p1:
// p1 instance values:
// Name: Frank, Age: 32
// Value: 7878
// p2 instance values:
// Name: Sam, Age: 42
// Value: 7878
//
// Values of p1 and p3 after changes to p1:
// p1 instance values:
// Name: George, Age: 39
// Value: 8641
// p3 instance values:
// Name: Frank, Age: 32
// Value: 7878
Public Class IdInfo
Public IdNumber As Integer
Public Sub New(IdNumber As Integer)
Me.IdNumber = IdNumber
End Sub
End Class
Public Class Person
Public Age As Integer
Public Name As String
Public IdInfo As IdInfo
Public Function ShallowCopy() As Person
Return DirectCast(Me.MemberwiseClone(), Person)
End Function
Public Function DeepCopy() As Person
Dim other As Person = DirectCast(Me.MemberwiseClone(), Person)
other.IdInfo = New IdInfo(IdInfo.IdNumber)
other.Name = String.Copy(Name)
Return other
End Function
End Class
Module Example
Public Sub Main()
' Create an instance of Person and assign values to its fields.
Dim p1 As New Person()
p1.Age = 42
p1.Name = "Sam"
p1.IdInfo = New IdInfo(6565)
' Perform a shallow copy of p1 and assign it to p2.
Dim p2 As Person = p1.ShallowCopy()
' Display values of p1, p2
Console.WriteLine("Original values of p1 and p2:")
Console.WriteLine(" p1 instance values: ")
DisplayValues(p1)
Console.WriteLine(" p2 instance values:")
DisplayValues(p2)
Console.WriteLine()
' Change the value of p1 properties and display the values of p1 and p2.
p1.Age = 32
p1.Name = "Frank"
p1.IdInfo.IdNumber = 7878
Console.WriteLine("Values of p1 and p2 after changes to p1:")
Console.WriteLine(" p1 instance values: ")
DisplayValues(p1)
Console.WriteLine(" p2 instance values:")
DisplayValues(p2)
Console.WriteLine()
' Make a deep copy of p1 and assign it to p3.
Dim p3 As Person = p1.DeepCopy()
' Change the members of the p1 class to new values to show the deep copy.
p1.Name = "George"
p1.Age = 39
p1.IdInfo.IdNumber = 8641
Console.WriteLine("Values of p1 and p3 after changes to p1:")
Console.WriteLine(" p1 instance values: ")
DisplayValues(p1)
Console.WriteLine(" p3 instance values:")
DisplayValues(p3)
End Sub
Public Sub DisplayValues(p As Person)
Console.WriteLine(" Name: {0:s}, Age: {1:d}", p.Name, p.Age)
Console.WriteLine(" Value: {0:d}", p.IdInfo.IdNumber)
End Sub
End Module
' The example displays the following output:
' Original values of m1 and m2:
' m1 instance values:
' Name: Sam, Age: 42
' Value: 6565
' m2 instance values:
' Name: Sam, Age: 42
' Value: 6565
'
' Values of m1 and m2 after changes to m1:
' m1 instance values:
' Name: Frank, Age: 32
' Value: 7878
' m2 instance values:
' Name: Sam, Age: 42
' Value: 7878
'
' Values of m1 and m3 after changes to m1:
' m1 instance values:
' Name: George, Age: 39
' Value: 8641
' m3 instance values:
' Name: Frank, Age: 32
' Value: 7878
En este ejemplo, la Person.IdInfo
propiedad devuelve un IdInfo
objeto.In this example, the Person.IdInfo
property returns an IdInfo
object. Como se muestra en el resultado del ejemplo, cuando Person
se clona un objeto llamando al MemberwiseClone método, el objeto clonado Person
es una copia independiente del objeto original, con la salvedad de que comparten la misma Person.IdInfo
referencia de objeto.As the output from the example shows, when a Person
object is cloned by calling the MemberwiseClone method, the cloned Person
object is an independent copy of the original object, except that they share the same Person.IdInfo
object reference. Como resultado, la modificación de la propiedad del clon Person.IdInfo
cambia la propiedad del objeto original Person.IdInfo
.As a result, modifying the clone's Person.IdInfo
property changes the original object's Person.IdInfo
property. Por otro lado, cuando se realiza una operación de copia en profundidad, el objeto clonado Person
, incluida su Person.IdInfo
propiedad, se puede modificar sin que ello afecte al objeto original.On the other hand, when a deep copy operation is performed, the cloned Person
object, including its Person.IdInfo
property, can be modified without affecting the original object.
Comentarios
El MemberwiseClone método crea una copia superficial creando un nuevo objeto y, a continuación, copiando los campos no estáticos del objeto actual en el nuevo objeto.The MemberwiseClone method creates a shallow copy by creating a new object, and then copying the nonstatic fields of the current object to the new object. Si un campo es un tipo de valor, se realiza una copia bit a bit del campo.If a field is a value type, a bit-by-bit copy of the field is performed. Si un campo es un tipo de referencia, la referencia se copia pero no el objeto al que se hace referencia; por lo tanto, el objeto original y su clonación hacen referencia al mismo objeto.If a field is a reference type, the reference is copied but the referred object is not; therefore, the original object and its clone refer to the same object.
Por ejemplo, considere un objeto denominado X que hace referencia a los objetos A y B. el objeto B, a su vez, hace referencia al objeto C. Una copia superficial de X crea un nuevo objeto x2 que también hace referencia a los objetos A y B. En cambio, una copia en profundidad de X crea un nuevo objeto x2 que hace referencia a los nuevos objetos a2 y B2, que son copias de A y B. B2, a su vez, hace referencia al nuevo objeto C2, que es una copia de C. En el ejemplo se muestra la diferencia entre una operación de copia superficial y en profundidad.For example, consider an object called X that references objects A and B. Object B, in turn, references object C. A shallow copy of X creates new object X2 that also references objects A and B. In contrast, a deep copy of X creates a new object X2 that references the new objects A2 and B2, which are copies of A and B. B2, in turn, references the new object C2, which is a copy of C. The example illustrates the difference between a shallow and a deep copy operation.
Hay varias maneras de implementar una operación de copia en profundidad si la operación de copia superficial realizada por el MemberwiseClone método no satisface sus necesidades.There are numerous ways to implement a deep copy operation if the shallow copy operation performed by the MemberwiseClone method does not meet your needs. Entre ellas, se incluyen las siguientes:These include the following:
Llame a un constructor de clase del objeto que se va a copiar para crear un segundo objeto con los valores de propiedad tomados del primer objeto.Call a class constructor of the object to be copied to create a second object with property values taken from the first object. Se supone que los valores de un objeto se definen por completo mediante su constructor de clase.This assumes that the values of an object are entirely defined by its class constructor.
Llame al MemberwiseClone método para crear una copia superficial de un objeto y, a continuación, asigne nuevos objetos cuyos valores sean los mismos que el objeto original a cualquier propiedad o campo cuyos valores sean tipos de referencia.Call the MemberwiseClone method to create a shallow copy of an object, and then assign new objects whose values are the same as the original object to any properties or fields whose values are reference types. El
DeepCopy
método en el ejemplo muestra este enfoque.TheDeepCopy
method in the example illustrates this approach.Serialice el objeto que se va a copiar en profundidad y, a continuación, restaure los datos serializados en una variable de objeto diferente.Serialize the object to be deep copied, and then restore the serialized data to a different object variable.
Use la reflexión con recursividad para realizar la operación de copia en profundidad.Use reflection with recursion to perform the deep copy operation.