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

下面是一个深度拷贝实现:

public static object CloneObject(object opSource)
{
    //grab the type and create a new instance of that type
    Type opSourceType = opSource.GetType();
    object opTarget = CreateInstanceOfType(opSourceType);

    //grab the properties
    PropertyInfo[] opPropertyInfo = opSourceType.GetProperties(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);

    //iterate over the properties and if it has a 'set' method assign it from the source TO the target
    foreach (PropertyInfo item in opPropertyInfo)
    {
        if (item.CanWrite)
        {
            //value types can simply be 'set'
            if (item.PropertyType.IsValueType || item.PropertyType.IsEnum || item.PropertyType.Equals(typeof(System.String)))
            {
                item.SetValue(opTarget, item.GetValue(opSource, null), null);
            }
            //object/complex types need to recursively call this method until the end of the tree is reached
            else
            {
                object opPropertyValue = item.GetValue(opSource, null);
                if (opPropertyValue == null)
                {
                    item.SetValue(opTarget, null, null);
                }
                else
                {
                    item.SetValue(opTarget, CloneObject(opPropertyValue), null);
                }
            }
        }
    }
    //return the new item
    return opTarget;
}

其他回答

最短的方式,但需要依赖:

using Newtonsoft.Json;
    public static T Clone<T>(T source) =>
        JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source));

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);
    }
}

通常,您实现ICloneable接口并自己实现克隆。C#对象有一个内置的MemberwiseColone方法,该方法执行浅层复制,可以帮助您处理所有原语。

对于深度复制,它无法知道如何自动执行。

由于我在不同的项目中找不到满足我所有需求的克隆器,我创建了一个可以配置并适应不同代码结构的深度克隆器,而不是调整我的代码以满足克隆器的需求。这是通过向要克隆的代码添加注释来实现的,或者您只需保留代码的默认行为。它使用反射、类型缓存并基于fasterflect。对于大量数据和高对象层次结构(与其他基于反射/序列化的算法相比),克隆过程非常快。

https://github.com/kalisohn/CloneBehave

也可作为nuget包提供:https://www.nuget.org/packages/Clone.Behave/1.0.0

例如:以下代码将执行deepCloneAddress,但只执行_currentJob字段的浅拷贝。

public class Person 
{
  [DeepClone(DeepCloneBehavior.Shallow)]
  private Job _currentJob;      

  public string Name { get; set; }

  public Job CurrentJob 
  { 
    get{ return _currentJob; }
    set{ _currentJob = value; }
  }

  public Person Manager { get; set; }
}

public class Address 
{      
  public Person PersonLivingHere { get; set; }
}

Address adr = new Address();
adr.PersonLivingHere = new Person("John");
adr.PersonLivingHere.BestFriend = new Person("James");
adr.PersonLivingHere.CurrentJob = new Job("Programmer");

Address adrClone = adr.Clone();

//RESULT
adr.PersonLivingHere == adrClone.PersonLivingHere //false
adr.PersonLivingHere.Manager == adrClone.PersonLivingHere.Manager //false
adr.PersonLivingHere.CurrentJob == adrClone.PersonLivingHere.CurrentJob //true
adr.PersonLivingHere.CurrentJob.AnyProperty == adrClone.PersonLivingHere.CurrentJob.AnyProperty //true

我知道,这个问题和答案在这里停留了一段时间,下面不是很好的答案,而是观察,最近我在检查是否确实没有克隆隐私(如果没有,我就不会是我自己了;)时,我很高兴地复制了粘贴的@johnc更新的答案。

我简单地制作了自己的扩展方法(这几乎是上述答案的复制粘贴):

public static class CloneThroughJsonExtension
{
    private static readonly JsonSerializerSettings DeserializeSettings = new JsonSerializerSettings { ObjectCreationHandling = ObjectCreationHandling.Replace };

    public static T CloneThroughJson<T>(this T source)
    {
        return ReferenceEquals(source, null) ? default(T) : JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source), DeserializeSettings);
    }
}

并天真地放弃了这样的课程(事实上,有更多这样的课程,但它们是无关的):

public class WhatTheHeck
{
    public string PrivateSet { get; private set; } // matches ctor param name

    public string GetOnly { get; } // matches ctor param name

    private readonly string _indirectField;
    public string Indirect => $"Inception of: {_indirectField} "; // matches ctor param name
    public string RealIndirectFieldVaule => _indirectField;

    public WhatTheHeck(string privateSet, string getOnly, string indirect)
    {
        PrivateSet = privateSet;
        GetOnly = getOnly;
        _indirectField = indirect;
    }
}

代码如下:

var clone = new WhatTheHeck("Private-Set-Prop cloned!", "Get-Only-Prop cloned!", "Indirect-Field clonned!").CloneThroughJson();
Console.WriteLine($"1. {clone.PrivateSet}");
Console.WriteLine($"2. {clone.GetOnly}");
Console.WriteLine($"3.1. {clone.Indirect}");
Console.WriteLine($"3.2. {clone.RealIndirectFieldVaule}");

结果是:

1. Private-Set-Prop cloned!
2. Get-Only-Prop cloned!
3.1. Inception of: Inception of: Indirect-Field cloned!
3.2. Inception of: Indirect-Field cloned!

我整个人都在想:什么……所以我抓起Newtonsoft.Json Github repo,开始挖掘。结果是:当反序列化一个恰好只有一个ctor且其参数名匹配(不区分大小写)公共属性名的类型时,它们将作为这些参数传递给ctor。在这里和这里的代码中可以找到一些线索。

要旨

我知道这不是很常见的情况,示例代码有点滥用,但嘿!当我检查灌木丛中是否有龙在等着跳出来咬我的屁股时,我大吃一惊;)