Objekte clonen

Es ist manchmal notwendig, den Inhalt eines bestehenden Objektes in ein neues Objekt zu kopieren. Eine einfache Zuweisung zweier mit new erzeugter Elemente übergibt nur die Referenz, nicht den Inhalt an ein neues Objekt. Es wird entweder ein Kopierkonstruktor benötigt oder es kann auch die Methode Clone() für ein Objekt implementiert werden, das Objekt muss dabei von ICloneable abgeleitet worden sein. Clone() erzeugt dabei ein neues Objekt der Klasse mit den kopierten Eigenschaften.

class TMyClass : ICloneable
{
   public double a;
   public double b;

   // Standardkontruktor
   public TMyClass()
   {
       this.a = 0.0;
       this.b = 0.0;
   }

   // Kopierkonstruktor
   public TMyClass(TMyClass MC)
   {
       this.a = MC.a;
       this.b = MC.b;
   }

   // Clonefunktion, muss Typ Object zurückgeben
   public Object Clone()
   {
       return new TMyClass(this);
   }
}

// Aufrufbeispiel für Clone()
TMyClass MyObject1 = new TMyClass();
TMyClass MyObject2 = null;

MyObject2 = MyObject1.Clone() as TMyClass;

// einfacher
TMyClass MyObject1 = new TMyClass();
TMyClass MyObject2 = new TMyClass(MyObject1);

Eine weitaus elegantere Methode lässt sich über die .NET-internen Mechanismen realisieren. Im nachstehenden Beispiel wird über Activator ein Objekt von beliebigem Typ erzeugt und dessen öffentliche Eigenschaften kopiert: Quelle auf Java2s und CallButler

///////////////////////////////////////////////////////////////////////////////////////////////
//
//    This File is Part of the CallButler Open Source PBX (http://www.codeplex.com/callbutler)
//
//    Copyright (c) 2005-2008, Jim Heising
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//    * Redistributions of source code must retain the above copyright notice,
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///////////////////////////////////////////////////////////////////////////////////////////////

using System;
using System.Collections.Generic;
using System.Text;

namespace WOSI.Utilities
{
    public class ObjectUtils
    {
        public static object Clone(object objectToClone)
        {
            object dataObject = Activator.CreateInstance(objectToClone.GetType());

            // Fill in our class fields
            foreach (System.Reflection.FieldInfo field in dataObject.GetType().GetFields())
            {
                try
                {
                    if (field.IsPublic)
                    {
                        field.SetValue(dataObject, objectToClone.GetType().GetField(field.Name).GetValue(objectToClone));
                    }
                }
                catch
                {
                }
            }

            // Fill in our class properties
            foreach (System.Reflection.PropertyInfo property in dataObject.GetType().GetProperties())
            {
                try
                {
                    if (property.PropertyType.IsPublic && property.CanWrite)
                    {
                        property.SetValue(dataObject, objectToClone.GetType().GetProperty(property.Name).GetValue(objectToClone, null), null);
                    }
                }
                catch
                {
                }
            }

            return dataObject;
        }
    }
}

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