Object.MemberwiseClone Object.MemberwiseClone Object.MemberwiseClone Object.MemberwiseClone Method

定義

現在の Object の簡易コピーを作成します。 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

戻り値

現在の Object の簡易コピー。 A shallow copy of the current Object.

次の例を示しています、MemberwiseCloneメソッド。The following example illustrates the MemberwiseClone method. 定義、ShallowCopyメソッドを呼び出す、MemberwiseClone簡易コピー操作を実行するメソッド、Personオブジェクト。It defines a ShallowCopy method that calls the MemberwiseClone method to perform a shallow copy operation on a Person object. 定義、DeepCopyに対してディープ コピー操作を実行するメソッド、Personオブジェクト。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

この例で、Person.IdInfoプロパティが返す、IdInfoオブジェクト。In this example, the Person.IdInfo property returns an IdInfo object. 例を示しますから出力としてときに、Personオブジェクトが呼び出すことによって複製、MemberwiseCloneメソッドは、複製されたPersonオブジェクトには、元のオブジェクトの独立したコピーがある同じ共有をPerson.IdInfoオブジェクト参照。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. その結果、クローンの変更するPerson.IdInfoプロパティが変更元のオブジェクトのPerson.IdInfoプロパティ。As a result, modifying the clone's Person.IdInfo property changes the original object's Person.IdInfo property. その一方で、詳細コピー操作を実行ときに、複製されたPersonオブジェクトを含むそのPerson.IdInfoプロパティは、元のオブジェクトの影響を与えずに変更できます。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.

注釈

MemberwiseCloneメソッドは、新しいオブジェクトを作成し、新しいオブジェクトを現在のオブジェクトの非静的フィールドをコピーして簡易コピーを作成します。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. フィールドが値型の場合は、フィールドのビットごとのコピーが実行されます。If a field is a value type, a bit-by-bit copy of the field is performed. フィールドが参照型の場合は、参照がコピーされますが、参照先オブジェクトがないです。そのため、元のオブジェクトとその複製は、同じオブジェクトを参照します。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.

たとえば、オブジェクト A と B をさらに、参照の参照オブジェクト C X という名前のオブジェクトX の簡易コピーは、オブジェクト A と B を参照する新しいオブジェクト X2 を作成します。これに対し、X の詳細コピーが A2 および B2、A のコピーは、新しいオブジェクトを参照する新しいオブジェクト X2 を作成し、B. B2、さらに、c ドライブのコピーである新しいオブジェクト C2 を参照この例では、shallow とディープ コピー操作の違いを示します。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.

簡易コピー操作を実行している場合、詳細コピー操作を実装する方法はたくさんあります、MemberwiseCloneメソッドは、ニーズを満たしていません。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. 次に例を示します。These include the following:

  • 最初のオブジェクトから取得したプロパティ値を 2 番目のオブジェクトを作成するコピーされるオブジェクトのクラスのコンス トラクターを呼び出します。Call a class constructor of the object to be copied to create a second object with property values taken from the first object. これは、そのクラス コンス トラクターによってオブジェクトの値がまったく定義されていると仮定します。This assumes that the values of an object are entirely defined by its class constructor.

  • 呼び出す、MemberwiseCloneメソッドをオブジェクトの簡易コピーを作成し、値は、プロパティやフィールドは参照型の値が元のオブジェクトと同じ新しいオブジェクトを割り当てます。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. DeepCopyメソッドの例では、この方法を示します。The DeepCopy method in the example illustrates this approach.

  • コピーには、ディープ オブジェクトをシリアル化し、別のオブジェクト変数をシリアル化されたデータを復元します。Serialize the object to be deep copied, and then restore the serialized data to a different object variable.

  • 再帰でリフレクションを使用して、詳細コピー操作を実行します。Use reflection with recursion to perform the deep copy operation.

適用対象