我想做一些事情,比如:

MyObject myObj = GetMyObj(); // Create and fill a new object
MyObject newObj = myObj.Clone();

然后对未反映在原始对象中的新对象进行更改。

我通常不需要这个功能,所以当有必要时,我会创建一个新对象,然后单独复制每个属性,但这总是让我觉得有更好或更优雅的方法来处理这种情况。

如何克隆或深度复制对象,以便在原始对象中不反映任何更改的情况下修改克隆的对象?


当前回答

使用IClonable接口可以花费多少精力是令人难以置信的,尤其是当您有大量的类层次结构时。MemberwiseColone的工作方式也很奇怪——它甚至不能完全克隆普通的List类型的结构。

当然,串行化最有趣的困境是串行化反向引用——例如,具有子-父关系的类层次结构。我怀疑二进制序列化程序能否在这种情况下帮助您。(最终将导致递归循环+堆栈溢出)。

不知怎么的,我喜欢这里提出的解决方案:如何在.NET(特别是C#)中对对象进行深度复制?

然而,它不支持Lists,并补充说,该支持还考虑到了重新养育子女的问题。对于我制定的仅为父项的规则,该字段或属性应命名为“parent”,则DeepClone将忽略它。您可能需要决定自己的反向引用规则——对于树层次结构,它可能是“左/右”等。。。

以下是包含测试代码的完整代码片段:

using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Reflection;
using System.Text;

namespace TestDeepClone
{
    class Program
    {
        static void Main(string[] args)
        {
            A a = new A();
            a.name = "main_A";
            a.b_list.Add(new B(a) { name = "b1" });
            a.b_list.Add(new B(a) { name = "b2" });

            A a2 = (A)a.DeepClone();
            a2.name = "second_A";

            // Perform re-parenting manually after deep copy.
            foreach( var b in a2.b_list )
                b.parent = a2;


            Debug.WriteLine("ok");

        }
    }

    public class A
    {
        public String name = "one";
        public List<String> list = new List<string>();
        public List<String> null_list;
        public List<B> b_list = new List<B>();
        private int private_pleaseCopyMeAsWell = 5;

        public override string ToString()
        {
            return "A(" + name + ")";
        }
    }

    public class B
    {
        public B() { }
        public B(A _parent) { parent = _parent; }
        public A parent;
        public String name = "two";
    }


    public static class ReflectionEx
    {
        public static Type GetUnderlyingType(this MemberInfo member)
        {
            Type type;
            switch (member.MemberType)
            {
                case MemberTypes.Field:
                    type = ((FieldInfo)member).FieldType;
                    break;
                case MemberTypes.Property:
                    type = ((PropertyInfo)member).PropertyType;
                    break;
                case MemberTypes.Event:
                    type = ((EventInfo)member).EventHandlerType;
                    break;
                default:
                    throw new ArgumentException("member must be if type FieldInfo, PropertyInfo or EventInfo", "member");
            }
            return Nullable.GetUnderlyingType(type) ?? type;
        }

        /// <summary>
        /// Gets fields and properties into one array.
        /// Order of properties / fields will be preserved in order of appearance in class / struct. (MetadataToken is used for sorting such cases)
        /// </summary>
        /// <param name="type">Type from which to get</param>
        /// <returns>array of fields and properties</returns>
        public static MemberInfo[] GetFieldsAndProperties(this Type type)
        {
            List<MemberInfo> fps = new List<MemberInfo>();
            fps.AddRange(type.GetFields());
            fps.AddRange(type.GetProperties());
            fps = fps.OrderBy(x => x.MetadataToken).ToList();
            return fps.ToArray();
        }

        public static object GetValue(this MemberInfo member, object target)
        {
            if (member is PropertyInfo)
            {
                return (member as PropertyInfo).GetValue(target, null);
            }
            else if (member is FieldInfo)
            {
                return (member as FieldInfo).GetValue(target);
            }
            else
            {
                throw new Exception("member must be either PropertyInfo or FieldInfo");
            }
        }

        public static void SetValue(this MemberInfo member, object target, object value)
        {
            if (member is PropertyInfo)
            {
                (member as PropertyInfo).SetValue(target, value, null);
            }
            else if (member is FieldInfo)
            {
                (member as FieldInfo).SetValue(target, value);
            }
            else
            {
                throw new Exception("destinationMember must be either PropertyInfo or FieldInfo");
            }
        }

        /// <summary>
        /// Deep clones specific object.
        /// Analogue can be found here: https://stackoverflow.com/questions/129389/how-do-you-do-a-deep-copy-an-object-in-net-c-specifically
        /// This is now improved version (list support added)
        /// </summary>
        /// <param name="obj">object to be cloned</param>
        /// <returns>full copy of object.</returns>
        public static object DeepClone(this object obj)
        {
            if (obj == null)
                return null;

            Type type = obj.GetType();

            if (obj is IList)
            {
                IList list = ((IList)obj);
                IList newlist = (IList)Activator.CreateInstance(obj.GetType(), list.Count);

                foreach (object elem in list)
                    newlist.Add(DeepClone(elem));

                return newlist;
            } //if

            if (type.IsValueType || type == typeof(string))
            {
                return obj;
            }
            else if (type.IsArray)
            {
                Type elementType = Type.GetType(type.FullName.Replace("[]", string.Empty));
                var array = obj as Array;
                Array copied = Array.CreateInstance(elementType, array.Length);

                for (int i = 0; i < array.Length; i++)
                    copied.SetValue(DeepClone(array.GetValue(i)), i);

                return Convert.ChangeType(copied, obj.GetType());
            }
            else if (type.IsClass)
            {
                object toret = Activator.CreateInstance(obj.GetType());

                MemberInfo[] fields = type.GetFieldsAndProperties();
                foreach (MemberInfo field in fields)
                {
                    // Don't clone parent back-reference classes. (Using special kind of naming 'parent' 
                    // to indicate child's parent class.
                    if (field.Name == "parent")
                    {
                        continue;
                    }

                    object fieldValue = field.GetValue(obj);

                    if (fieldValue == null)
                        continue;

                    field.SetValue(toret, DeepClone(fieldValue));
                }

                return toret;
            }
            else
            {
                // Don't know that type, don't know how to clone it.
                if (Debugger.IsAttached)
                    Debugger.Break();

                return null;
            }
        } //DeepClone
    }

}

其他回答

基本上,您需要实现ICloneable接口,然后实现对象结构复制。如果它是所有成员的深度拷贝,您需要确保(与您选择的解决方案无关)所有子级都是可克隆的。有时,在这个过程中,您需要注意一些限制,例如,如果您复制ORM对象,大多数框架只允许一个对象附加到会话,并且您不能克隆该对象,或者如果可能,您需要关注这些对象的会话附加。

干杯

通用方法在技术上都是有效的,但我只想补充一点,因为我们实际上很少需要真正的深度复制,我强烈反对在实际的业务应用程序中使用通用深度复制,因为这使得您可能会在许多地方复制对象,然后显式修改,这很容易丢失。

在大多数实际情况下,您还希望对复制过程进行尽可能多的粒度控制,因为您不仅耦合到数据访问框架,而且在实践中,复制的业务对象几乎不应该100%相同。举一个ORM用来识别对象引用的referenceId的例子,一个完整的深度副本也会复制这个id,所以在内存中,对象会不同,一旦你将其提交到数据存储,它就会抱怨,因此,无论如何,您都必须在复制后手动修改此财产,如果对象发生更改,则需要在使用通用深度复制的所有位置对其进行调整。

用ICloneable扩展@cregox答案,到底什么是深度副本?它只是堆上新分配的一个对象,与原始对象相同,但占用不同的内存空间,而不是使用通用的克隆器功能,为什么不创建一个新对象呢?

我个人在我的域对象上使用静态工厂方法的思想。

例子:

    public class Client
    {
        public string Name { get; set; }

        protected Client()
        {
        }

        public static Client Clone(Client copiedClient)
        {
            return new Client
            {
                Name = copiedClient.Name
            };
        }
    }

    public class Shop
    {
        public string Name { get; set; }

        public string Address { get; set; }

        public ICollection<Client> Clients { get; set; }

        public static Shop Clone(Shop copiedShop, string newAddress, ICollection<Client> clients)
        {
            var copiedClients = new List<Client>();
            foreach (var client in copiedShop.Clients)
            {
                copiedClients.Add(Client.Clone(client));
            }

            return new Shop
            {
                Name = copiedShop.Name,
                Address = newAddress,
                Clients = copiedClients
            };
        }
    }

如果有人在研究如何在保持对复制过程的完全控制的同时构建对象实例化,这是我个人非常成功的解决方案。受保护的构造函数也使其成为可能,其他开发人员被迫使用工厂方法,该方法提供了一个简洁的单点对象实例化,封装了对象内部的构造逻辑。如果需要,您还可以重载该方法,并为不同的位置提供多个克隆逻辑。

我在Silverlight中使用ICloneable时遇到了问题,但我喜欢序列化的想法,我可以序列化XML,所以我这样做了:

static public class SerializeHelper
{
    //Michael White, Holly Springs Consulting, 2009
    //michael@hollyspringsconsulting.com
    public static T DeserializeXML<T>(string xmlData) 
        where T:new()
    {
        if (string.IsNullOrEmpty(xmlData))
            return default(T);

        TextReader tr = new StringReader(xmlData);
        T DocItms = new T();
        XmlSerializer xms = new XmlSerializer(DocItms.GetType());
        DocItms = (T)xms.Deserialize(tr);

        return DocItms == null ? default(T) : DocItms;
    }

    public static string SeralizeObjectToXML<T>(T xmlObject)
    {
        StringBuilder sbTR = new StringBuilder();
        XmlSerializer xmsTR = new XmlSerializer(xmlObject.GetType());
        XmlWriterSettings xwsTR = new XmlWriterSettings();
        
        XmlWriter xmwTR = XmlWriter.Create(sbTR, xwsTR);
        xmsTR.Serialize(xmwTR,xmlObject);
        
        return sbTR.ToString();
    }

    public static T CloneObject<T>(T objClone) 
        where T:new()
    {
        string GetString = SerializeHelper.SeralizeObjectToXML<T>(objClone);
        return SerializeHelper.DeserializeXML<T>(GetString);
    }
}

我喜欢这样的Copyconstructors:

    public AnyObject(AnyObject anyObject)
    {
        foreach (var property in typeof(AnyObject).GetProperties())
        {
            property.SetValue(this, property.GetValue(anyObject));
        }
        foreach (var field in typeof(AnyObject).GetFields())
        {
            field.SetValue(this, field.GetValue(anyObject));
        }
    }

如果您有更多内容要复制,请添加它们

C#扩展也将支持“not ISerializable”类型。

 public static class AppExtensions
 {                                                                      
       public static T DeepClone<T>(this T a)
       {
           using (var stream = new MemoryStream())
           {
               var serializer = new System.Xml.Serialization.XmlSerializer(typeof(T));

               serializer.Serialize(stream, a);
               stream.Position = 0;
               return (T)serializer.Deserialize(stream);
           }
       }                                                                    
 }

用法

       var obj2 = obj1.DeepClone()