Object.MemberwiseClone Method (System)

MemberwiseClone Method

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

Object..::.MemberwiseClone Method

Creates a shallow copy of the current Object.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

Syntax

Visual Basic (Declaration)

Protected Function MemberwiseClone As Object

Visual Basic (Usage)

Dim returnValue As Object

returnValue = Me.MemberwiseClone()

protected Object MemberwiseClone()

Visual C++

protected:
Object^ MemberwiseClone()

JScript

protected function MemberwiseClone() : Object

Return Value

Type: System..::.Object
A shallow copy of the current Object.

Remarks

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. If a field is a value type, a bit-by-bit copy of the field is performed. 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.

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 C. Use a class that implements the ICloneable interface to perform a deep or shallow copy of an object.

Examples

The following code example shows how to copy an instance of a class using MemberwiseClone.

Visual Basic

Imports System

Class MyBaseClass
   Public Shared CompanyName As String = "My Company"
   Public age As Integer
   Public name As String
End Class 'MyBaseClass

Class MyDerivedClass
   Inherits MyBaseClass

   Shared Sub Main()

      ' Creates an instance of MyDerivedClass and assign values to its fields.
      Dim m1 As New MyDerivedClass()
      m1.age = 42
      m1.name = "Sam"

      ' Performs a shallow copy of m1 and assign it to m2.
      Dim m2 As MyDerivedClass = CType(m1.MemberwiseClone(), MyDerivedClass)

   End Sub 'Main

End Class 'MyDerivedClass

using System;

class MyBaseClass {
   public static string CompanyName = "My Company";
   public int age;
   public string name;
}

class MyDerivedClass: MyBaseClass {

   static void Main() {

   // Creates an instance of MyDerivedClass and assign values to its fields.
   MyDerivedClass m1 = new MyDerivedClass();
   m1.age = 42;
   m1.name = "Sam";

   // Performs a shallow copy of m1 and assign it to m2.
   MyDerivedClass m2 = (MyDerivedClass) m1.MemberwiseClone();
   }
}

Visual C++

using namespace System;
ref class MyBaseClass
{
public:
   static String^ CompanyName;
   int age;
   String^ name;
};

ref class MyDerivedClass: public MyBaseClass
{
public:
   static void Test()
   {

      // Creates an instance of MyDerivedClass and assign values to its fields.
      MyDerivedClass^ m1 = gcnew MyDerivedClass;
      m1->age = 42;
      m1->name = "Sam";

      // Performs a shallow copy of m1 and assign it to m2.
      MyDerivedClass^ m2 = safe_cast<MyDerivedClass^>(m1->MemberwiseClone());
   }

};

int main()
{
   MyDerivedClass::Test();
}

import System.*;

class MyBaseClass implements ICloneable
{
    public static String companyName = "My Company";
    public int age;
    public String name;
} //MyBaseClass

class MyDerivedClass extends MyBaseClass
{
    public static void main(String[] args) throws CloneNotSupportedException
    {
        // Creates an instance of MyDerivedClass and assign 
        // values to its fields.
        MyDerivedClass m1 = new MyDerivedClass();
        m1.age = 42;
        m1.name = "Sam";

        // Performs a shallow copy of m1 and assign it to m2.
        MyDerivedClass m2 = (MyDerivedClass)m1.MemberwiseClone();
    } //main
} //MyDerivedClass

JScript

import System

class MyBaseClass {
   public static var CompanyName : String = "My Company";
   public var age : int;
   public var name : String;
}

class MyDerivedClass extends MyBaseClass {

   static function Main() {

   // Creates an instance of MyDerivedClass and assign values to its fields.
   var m1 : MyDerivedClass = new MyDerivedClass();
   m1.age = 42;
   m1.name = "Sam";

   // Performs a shallow copy of m1 and assign it to m2.
   var m2 : MyDerivedClass = MyDerivedClass(m1.MemberwiseClone());
   }
}

Platforms

Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information