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 // All rights reserved. // // Redistribution and use in source and binary forms, with or without modification, // are permitted provided that the following conditions are met: // // * Redistributions of source code must retain the above copyright notice, // this list of conditions and the following disclaimer. // // * Redistributions in binary form must reproduce the above copyright notice, // this list of conditions and the following disclaimer in the documentation and/or // other materials provided with the distribution. // // * Neither the name of Jim Heising nor the names of its contributors may be // used to endorse or promote products derived from this software without specific prior // written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. // IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, // INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT // NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, // WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE // POSSIBILITY OF SUCH DAMAGE. // /////////////////////////////////////////////////////////////////////////////////////////////// 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; } } }