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?
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
由于这个问题的几乎所有答案都不令人满意,或者在我的情况下显然不起作用,我编写了AnyClone,它完全通过反思实现,并解决了这里的所有需求。我无法让序列化在结构复杂的复杂场景中工作,IClonable也不太理想——事实上,它甚至没有必要。
使用[IgnoreDataMember]、[NonSerialized]支持标准忽略属性。支持复杂集合、不带setter的财产、只读字段等。
我希望这能帮助其他遇到我同样问题的人。
其他回答
代码生成器
我们已经看到了很多想法,从序列化到手动实现再到反射,我想使用CGbR代码生成器提出一种完全不同的方法。生成克隆方法具有内存和CPU效率,因此比标准DataContractSerializer快300倍。
你只需要一个带有ICloneable的部分类定义,生成器就可以完成剩下的工作:
public partial class Root : ICloneable
{
public Root(int number)
{
_number = number;
}
private int _number;
public Partial[] Partials { get; set; }
public IList<ulong> Numbers { get; set; }
public object Clone()
{
return Clone(true);
}
private Root()
{
}
}
public partial class Root
{
public Root Clone(bool deep)
{
var copy = new Root();
// All value types can be simply copied
copy._number = _number;
if (deep)
{
// In a deep clone the references are cloned
var tempPartials = new Partial[Partials.Length];
for (var i = 0; i < Partials.Length; i++)
{
var value = Partials[i];
value = value.Clone(true);
tempPartials[i] = value;
}
copy.Partials = tempPartials;
var tempNumbers = new List<ulong>(Numbers.Count);
for (var i = 0; i < Numbers.Count; i++)
{
var value = Numbers[i];
tempNumbers.Add(value);
}
copy.Numbers = tempNumbers;
}
else
{
// In a shallow clone only references are copied
copy.Partials = Partials;
copy.Numbers = Numbers;
}
return copy;
}
}
注意:最新版本有更多的空检查,但为了更好地理解,我省略了它们。
这里有一个快速而简单的解决方案,不依赖于序列化/反序列化。
public class MyClass
{
public virtual MyClass DeepClone()
{
var returnObj = (MyClass)MemberwiseClone();
var type = returnObj.GetType();
var fieldInfoArray = type.GetRuntimeFields().ToArray();
foreach (var fieldInfo in fieldInfoArray)
{
object sourceFieldValue = fieldInfo.GetValue(this);
if (!(sourceFieldValue is MyClass))
{
continue;
}
var sourceObj = (MyClass)sourceFieldValue;
var clonedObj = sourceObj.DeepClone();
fieldInfo.SetValue(returnObj, clonedObj);
}
return returnObj;
}
}
编辑:要求
using System.Linq;
using System.Reflection;
我就是这么用的
public MyClass Clone(MyClass theObjectIneededToClone)
{
MyClass clonedObj = theObjectIneededToClone.DeepClone();
}
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
}
}
保持简单,并使用AutoMapper,正如其他人提到的,这是一个简单的小库,可以将一个对象映射到另一个对象。。。要将一个对象复制到另一个具有相同类型的对象,只需要三行代码:
MyType source = new MyType();
Mapper.CreateMap<MyType, MyType>();
MyType target = Mapper.Map<MyType, MyType>(source);
目标对象现在是源对象的副本。不够简单?创建扩展方法以在解决方案中的任何地方使用:
public static T Copy<T>(this T source)
{
T copy = default(T);
Mapper.CreateMap<T, T>();
copy = Mapper.Map<T, T>(source);
return copy;
}
扩展方法可以如下使用:
MyType copy = source.Copy();
我想你可以试试这个。
MyObject myObj = GetMyObj(); // Create and fill a new object
MyObject newObj = new MyObject(myObj); //DeepClone it