Object.MemberwiseClone Método

Definición

Crea una copia superficial del Object actual.Creates a shallow copy of the current Object.

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 método ShallowCopy que llama al método MemberwiseClone para realizar una operación de copia superficial en un objeto Person.It defines a ShallowCopy method that calls the MemberwiseClone method to perform a shallow copy operation on a Person object. También define un método DeepCopy que realiza una operación de copia en profundidad en un objeto Person.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 propiedad Person.IdInfo devuelve un objeto IdInfo.In this example, the Person.IdInfo property returns an IdInfo object. Como se muestra en el resultado del ejemplo, cuando se clona un objeto Person llamando al método MemberwiseClone, el objeto clonado Person es una copia independiente del objeto original, con la salvedad de que comparten la misma referencia de objeto Person.IdInfo.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 Person.IdInfo del clon cambia la propiedad Person.IdInfo del objeto original.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 Person clonado, incluida su propiedad Person.IdInfo, 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 método MemberwiseClone 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 muchas maneras de implementar una operación de copia en profundidad si la operación de copia superficial realizada por el método MemberwiseClone 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 método MemberwiseClone 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. En el método DeepCopy del ejemplo se muestra este enfoque.The DeepCopy 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.

Se aplica a