对象拷贝 - c#深拷贝




深入克隆对象 (20)

我想要做一些事情:

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。

我不经常需要这个功能,所以当有必要的时候,我已经采取了创建一个新的对象,然后单独复制每个属性,但它总是让我感觉有一种更好或更优雅的处理方式情况。

如何克隆或深度复制对象,以便可以修改克隆的对象,而不会在原始对象中反映任何更改?


Code Generator

We have seen a lot of ideas from serialization over manual implementation to reflection and I want to propose a totally different approach using the CGbR Code Generator . The generate clone method is memory and CPU efficient and therefor 300x faster as the standard DataContractSerializer.

All you need is a partial class definition with ICloneable and the generator does the rest:

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;
    }
}

Note: Latest version has a more null checks, but I left them out for better understanding.


Q. Why would I choose this answer?

  • Choose this answer if you want the fastest speed .NET is capable of.
  • Ignore this answer if you want a really, really easy method of cloning.

In other words, go with another answer unless you have a performance bottleneck that needs fixing, and you can prove it with a profiler .

10x faster than other methods

The following method of performing a deep clone is:

  • 10x faster than anything that involves serialization/deserialization;
  • Pretty darn close to the theoretical maximum speed .NET is capable of.

And the method ...

For ultimate speed, you can use Nested MemberwiseClone to do a deep copy . Its almost the same speed as copying a value struct, and is much faster than (a) reflection or (b) serialization (as described in other answers on this page).

Note that if you use Nested MemberwiseClone for a deep copy , you have to manually implement a ShallowCopy for each nested level in the class, and a DeepCopy which calls all said ShallowCopy methods to create a complete clone. This is simple: only a few lines in total, see the demo code below.

Here is the output of the code showing the relative performance difference for 100,000 clones:

  • 1.08 seconds for Nested MemberwiseClone on nested structs
  • 4.77 seconds for Nested MemberwiseClone on nested classes
  • 39.93 seconds for Serialization/Deserialization

Using Nested MemberwiseClone on a class almost as fast as copying a struct, and copying a struct is pretty darn close to the theoretical maximum speed .NET is capable of.

Demo 1 of shallow and deep copy, using classes and MemberwiseClone:
  Create Bob
    Bob.Age=30, Bob.Purchase.Description=Lamborghini
  Clone Bob >> BobsSon
  Adjust BobsSon details
    BobsSon.Age=2, BobsSon.Purchase.Description=Toy car
  Proof of deep copy: If BobsSon is a true clone, then adjusting BobsSon details will not affect Bob:
    Bob.Age=30, Bob.Purchase.Description=Lamborghini
  Elapsed time: 00:00:04.7795670,30000000

Demo 2 of shallow and deep copy, using structs and value copying:
  Create Bob
    Bob.Age=30, Bob.Purchase.Description=Lamborghini
  Clone Bob >> BobsSon
  Adjust BobsSon details:
    BobsSon.Age=2, BobsSon.Purchase.Description=Toy car
  Proof of deep copy: If BobsSon is a true clone, then adjusting BobsSon details will not affect Bob:
    Bob.Age=30, Bob.Purchase.Description=Lamborghini
  Elapsed time: 00:00:01.0875454,30000000

Demo 3 of deep copy, using class and serialize/deserialize:
  Elapsed time: 00:00:39.9339425,30000000

To understand how to do a deep copy using MemberwiseCopy, here is the demo project that was used to generate the times above:

// Nested MemberwiseClone example. 
// Added to demo how to deep copy a reference class.
[Serializable] // Not required if using MemberwiseClone, only used for speed comparison using serialization.
public class Person
{
    public Person(int age, string description)
    {
        this.Age = age;
        this.Purchase.Description = description;
    }
    [Serializable] // Not required if using MemberwiseClone
    public class PurchaseType
    {
        public string Description;
        public PurchaseType ShallowCopy()
        {
            return (PurchaseType)this.MemberwiseClone();
        }
    }
    public PurchaseType Purchase = new PurchaseType();
    public int Age;
    // Add this if using nested MemberwiseClone.
    // This is a class, which is a reference type, so cloning is more difficult.
    public Person ShallowCopy()
    {
        return (Person)this.MemberwiseClone();
    }
    // Add this if using nested MemberwiseClone.
    // This is a class, which is a reference type, so cloning is more difficult.
    public Person DeepCopy()
    {
            // Clone the root ...
        Person other = (Person) this.MemberwiseClone();
            // ... then clone the nested class.
        other.Purchase = this.Purchase.ShallowCopy();
        return other;
    }
}
// Added to demo how to copy a value struct (this is easy - a deep copy happens by default)
public struct PersonStruct
{
    public PersonStruct(int age, string description)
    {
        this.Age = age;
        this.Purchase.Description = description;
    }
    public struct PurchaseType
    {
        public string Description;
    }
    public PurchaseType Purchase;
    public int Age;
    // This is a struct, which is a value type, so everything is a clone by default.
    public PersonStruct ShallowCopy()
    {
        return (PersonStruct)this;
    }
    // This is a struct, which is a value type, so everything is a clone by default.
    public PersonStruct DeepCopy()
    {
        return (PersonStruct)this;
    }
}
// Added only for a speed comparison.
public class MyDeepCopy
{
    public static T DeepCopy<T>(T obj)
    {
        object result = null;
        using (var ms = new MemoryStream())
        {
            var formatter = new BinaryFormatter();
            formatter.Serialize(ms, obj);
            ms.Position = 0;
            result = (T)formatter.Deserialize(ms);
            ms.Close();
        }
        return (T)result;
    }
}

Then, call the demo from main:

void MyMain(string[] args)
{
    {
        Console.Write("Demo 1 of shallow and deep copy, using classes and MemberwiseCopy:\n");
        var Bob = new Person(30, "Lamborghini");
        Console.Write("  Create Bob\n");
        Console.Write("    Bob.Age={0}, Bob.Purchase.Description={1}\n", Bob.Age, Bob.Purchase.Description);
        Console.Write("  Clone Bob >> BobsSon\n");
        var BobsSon = Bob.DeepCopy();
        Console.Write("  Adjust BobsSon details\n");
        BobsSon.Age = 2;
        BobsSon.Purchase.Description = "Toy car";
        Console.Write("    BobsSon.Age={0}, BobsSon.Purchase.Description={1}\n", BobsSon.Age, BobsSon.Purchase.Description);
        Console.Write("  Proof of deep copy: If BobsSon is a true clone, then adjusting BobsSon details will not affect Bob:\n");
        Console.Write("    Bob.Age={0}, Bob.Purchase.Description={1}\n", Bob.Age, Bob.Purchase.Description);
        Debug.Assert(Bob.Age == 30);
        Debug.Assert(Bob.Purchase.Description == "Lamborghini");
        var sw = new Stopwatch();
        sw.Start();
        int total = 0;
        for (int i = 0; i < 100000; i++)
        {
            var n = Bob.DeepCopy();
            total += n.Age;
        }
        Console.Write("  Elapsed time: {0},{1}\n\n", sw.Elapsed, total);
    }
    {               
        Console.Write("Demo 2 of shallow and deep copy, using structs:\n");
        var Bob = new PersonStruct(30, "Lamborghini");
        Console.Write("  Create Bob\n");
        Console.Write("    Bob.Age={0}, Bob.Purchase.Description={1}\n", Bob.Age, Bob.Purchase.Description);
        Console.Write("  Clone Bob >> BobsSon\n");
        var BobsSon = Bob.DeepCopy();
        Console.Write("  Adjust BobsSon details:\n");
        BobsSon.Age = 2;
        BobsSon.Purchase.Description = "Toy car";
        Console.Write("    BobsSon.Age={0}, BobsSon.Purchase.Description={1}\n", BobsSon.Age, BobsSon.Purchase.Description);
        Console.Write("  Proof of deep copy: If BobsSon is a true clone, then adjusting BobsSon details will not affect Bob:\n");
        Console.Write("    Bob.Age={0}, Bob.Purchase.Description={1}\n", Bob.Age, Bob.Purchase.Description);                
        Debug.Assert(Bob.Age == 30);
        Debug.Assert(Bob.Purchase.Description == "Lamborghini");
        var sw = new Stopwatch();
        sw.Start();
        int total = 0;
        for (int i = 0; i < 100000; i++)
        {
            var n = Bob.DeepCopy();
            total += n.Age;
        }
        Console.Write("  Elapsed time: {0},{1}\n\n", sw.Elapsed, total);
    }
    {
        Console.Write("Demo 3 of deep copy, using class and serialize/deserialize:\n");
        int total = 0;
        var sw = new Stopwatch();
        sw.Start();
        var Bob = new Person(30, "Lamborghini");
        for (int i = 0; i < 100000; i++)
        {
            var BobsSon = MyDeepCopy.DeepCopy<Person>(Bob);
            total += BobsSon.Age;
        }
        Console.Write("  Elapsed time: {0},{1}\n", sw.Elapsed, total);
    }
    Console.ReadKey();
}

Again, note that if you use Nested MemberwiseClone for a deep copy , you have to manually implement a ShallowCopy for each nested level in the class, and a DeepCopy which calls all said ShallowCopy methods to create a complete clone. This is simple: only a few lines in total, see the demo code above.

Value types vs. References Types

Note that when it comes to cloning an object, there is is a big difference between a " struct " and a " class ":

  • If you have a " struct ", it's a value type so you can just copy it, and the contents will be cloned (but it will only make a shallow clone unless you use the techniques in this post).
  • If you have a " class ", it's a reference type , so if you copy it, all you are doing is copying the pointer to it. To create a true clone, you have to be more creative, and use differences between value types and references types which creates another copy of the original object in memory.

See differences between value types and references types .

Checksums to aid in debugging

  • Cloning objects incorrectly can lead to very difficult-to-pin-down bugs. In production code, I tend to implement a checksum to double check that the object has been cloned properly, and hasn't been corrupted by another reference to it. This checksum can be switched off in Release mode.
  • I find this method quite useful: often, you only want to clone parts of the object, not the entire thing.

Really useful for decoupling many threads from many other threads

One excellent use case for this code is feeding clones of a nested class or struct into a queue, to implement the producer / consumer pattern.

  • We can have one (or more) threads modifying a class that they own, then pushing a complete copy of this class into a ConcurrentQueue .
  • We then have one (or more) threads pulling copies of these classes out and dealing with them.

This works extremely well in practice, and allows us to decouple many threads (the producers) from one or more threads (the consumers).

And this method is blindingly fast too: if we use nested structs, it's 35x faster than serializing/deserializing nested classes, and allows us to take advantage of all of the threads available on the machine.

更新

Apparently, ExpressMapper is as fast, if not faster, than hand coding such as above. I might have to see how they compare with a profiler.


As I couldn't find a cloner that meets all my requirements in different projects, I created a deep cloner that can be configured and adapted to different code structures instead of adapting my code to meet the cloners requirements. Its achieved by adding annotations to the code that shall be cloned or you just leave the code as it is to have the default behaviour. It uses reflection, type caches and is based on fasterflect . The cloning process is very fast for a huge amount of data and a high object hierarchy (compared to other reflection/serialization based algorithms).

https://github.com/kalisohn/CloneBehave

Also available as a nuget package: https://www.nuget.org/packages/Clone.Behave/1.0.0

For example: The following code will deepClone Address, but only perform a shallow copy of the _currentJob field.

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

Here a solution fast and easy that worked for me without relaying on Serialization/Deserialization.

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;
    }
}

EDIT : requires

    using System.Linq;
    using System.Reflection;

That's How I used it

public MyClass Clone(MyClass theObjectIneededToClone)
{
    MyClass clonedObj = theObjectIneededToClone.DeepClone();
}

I have created a version of the accepted answer that works with both '[Serializable]' and '[DataContract]'. It has been a while since I wrote it, but if I remember correctly [DataContract] needed a different serializer.

Requires System, System.IO, System.Runtime.Serialization, System.Runtime.Serialization.Formatters.Binary, System.Xml ;

public static class ObjectCopier
{

    /// <summary>
    /// Perform a deep Copy of an object that is marked with '[Serializable]' or '[DataContract]'
    /// </summary>
    /// <typeparam name="T">The type of object being copied.</typeparam>
    /// <param name="source">The object instance to copy.</param>
    /// <returns>The copied object.</returns>
    public static T Clone<T>(T source)
    {
        if (typeof(T).IsSerializable == true)
        {
            return CloneUsingSerializable<T>(source);
        }

        if (IsDataContract(typeof(T)) == true)
        {
            return CloneUsingDataContracts<T>(source);
        }

        throw new ArgumentException("The type must be Serializable or use DataContracts.", "source");
    }


    /// <summary>
    /// Perform a deep Copy of an object that is marked with '[Serializable]'
    /// </summary>
    /// <remarks>
    /// Found on http://.com/questions/78536/cloning-objects-in-c-sharp
    /// Uses code found on CodeProject, which allows free use in third party apps
    /// - http://www.codeproject.com/KB/tips/SerializedObjectCloner.aspx
    /// </remarks>
    /// <typeparam name="T">The type of object being copied.</typeparam>
    /// <param name="source">The object instance to copy.</param>
    /// <returns>The copied object.</returns>
    public static T CloneUsingSerializable<T>(T source)
    {
        if (!typeof(T).IsSerializable)
        {
            throw new ArgumentException("The type must be serializable.", "source");
        }

        // Don't serialize a null object, simply return the default for that object
        if (Object.ReferenceEquals(source, null))
        {
            return default(T);
        }

        IFormatter formatter = new BinaryFormatter();
        Stream stream = new MemoryStream();
        using (stream)
        {
            formatter.Serialize(stream, source);
            stream.Seek(0, SeekOrigin.Begin);
            return (T)formatter.Deserialize(stream);
        }
    }


    /// <summary>
    /// Perform a deep Copy of an object that is marked with '[DataContract]'
    /// </summary>
    /// <typeparam name="T">The type of object being copied.</typeparam>
    /// <param name="source">The object instance to copy.</param>
    /// <returns>The copied object.</returns>
    public static T CloneUsingDataContracts<T>(T source)
    {
        if (IsDataContract(typeof(T)) == false)
        {
            throw new ArgumentException("The type must be a data contract.", "source");
        }

        // ** Don't serialize a null object, simply return the default for that object
        if (Object.ReferenceEquals(source, null))
        {
            return default(T);
        }

        DataContractSerializer dcs = new DataContractSerializer(typeof(T));
        using(Stream stream = new MemoryStream())
        {
            using (XmlDictionaryWriter writer = XmlDictionaryWriter.CreateBinaryWriter(stream))
            {
                dcs.WriteObject(writer, source);
                writer.Flush();
                stream.Seek(0, SeekOrigin.Begin);
                using (XmlDictionaryReader reader = XmlDictionaryReader.CreateBinaryReader(stream, XmlDictionaryReaderQuotas.Max))
                {
                    return (T)dcs.ReadObject(reader);
                }
            }
        }
    }


    /// <summary>
    /// Helper function to check if a class is a [DataContract]
    /// </summary>
    /// <param name="type">The type of the object to check.</param>
    /// <returns>Boolean flag indicating if the class is a DataContract (true) or not (false) </returns>
    public static bool IsDataContract(Type type)
    {
        object[] attributes = type.GetCustomAttributes(typeof(DataContractAttribute), false);
        return attributes.Length == 1;
    }

} 

I like Copyconstructors like that:

    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));
        }
    }

If you have more things to copy add them


I've seen it implemented through reflection as well. Basically there was a method that would iterate through the members of an object and appropriately copy them to the new object. When it reached reference types or collections I think it did a recursive call on itself. Reflection is expensive, but it worked pretty well.


If your Object Tree is Serializeable you could also use something like this

static public MyClass Clone(MyClass myClass)
{
    MyClass clone;
    XmlSerializer ser = new XmlSerializer(typeof(MyClass), _xmlAttributeOverrides);
    using (var ms = new MemoryStream())
    {
        ser.Serialize(ms, myClass);
        ms.Position = 0;
        clone = (MyClass)ser.Deserialize(ms);
    }
    return clone;
}

be informed that this Solution is pretty easy but it's not as performant as other solutions may be.

And be sure that if the Class grows, there will still be only those fields cloned, which also get serialized.


Keep things simple and use AutoMapper as others mentioned, it's a simple little library to map one object to another... To copy an object to another with the same type, all you need is three lines of code:

MyType source = new MyType();
Mapper.CreateMap<MyType, MyType>();
MyType target = Mapper.Map<MyType, MyType>(source);

The target object is now a copy of the source object. Not simple enough? Create an extension method to use everywhere in your solution:

public static T Copy<T>(this T source)
{
    T copy = default(T);
    Mapper.CreateMap<T, T>();
    copy = Mapper.Map<T, T>(source);
    return copy;
}

By using the extension method, the three lines become one line:

MyType copy = source.Copy();

Ok, there are some obvious example with reflection in this post, BUT reflection is usually slow, until you start to cache it properly.

if you'll cache it properly, than it'll deep clone 1000000 object by 4,6s (measured by Watcher).

static readonly Dictionary<Type, PropertyInfo[]> ProperyList = new Dictionary<Type, PropertyInfo[]>();

than you take cached properties or add new to dictionary and use them simply

foreach (var prop in propList)
{
        var value = prop.GetValue(source, null);   
        prop.SetValue(copyInstance, value, null);
}

full code check in my post in another answer

https://.com/a/34365709/4711853


To clone your class object you can use the Object.MemberwiseClone method,

just add this function to your class :

public class yourClass
{
    // ...
    // ...

    public yourClass DeepCopy()
    {
        yourClass othercopy = (yourClass)this.MemberwiseClone();
        return othercopy;
    }
}

then to perform a deep independant copy, just call the DeepCopy method :

yourClass newLine = oldLine.DeepCopy();

hope this helps.


不使用ICloneable的原因不是因为它没有通用接口。 不使用它的原因是因为它含糊不清 。 它并没有说明你是否得到浅或深的副本; 这取决于实施者。

是的, MemberwiseClone创建一个浅拷贝,但MemberwiseClone的对面不是Clone ; 它可能是DeepClone ,它不存在。 当您通过ICloneable接口使用对象时,无法知道底层对象执行哪种克隆。 (XML注释不会清楚,因为您将获得接口注释而不是对象的Clone方法。)

我通常做的只是制作一个Copy方法,它完全符合我的需求。


如果你想真正克隆到未知类型,你可以看看fastclone

这是基于表达式的克隆工作比二进制序列化快10倍,并保持完整的对象图完整性。

这意味着:如果多次引用您的层次中的同一个对象,那么这个克隆也会有一个被引用的实例。

不需要接口,属性或对被克隆对象的任何其他修改。


如果您已经在使用ValueInjecterValueInjecter等第三方应用程序,那么可以这样做:

MyObject oldObj; // The existing object to clone

MyObject newObj = new MyObject();
newObj.InjectFrom(oldObj); // Using ValueInjecter syntax

使用此方法,您不必在对象上实现ISerializable或ICloneable。 这在MVC / MVVM模式中很常见,所以创建了这样简单的工具。

请参阅CodePlex上的valueinjeter深度克隆解决方案


我想出了这个来克服.NET缺点,不得不手动深度复制List <T>。

我使用这个:

static public IEnumerable<SpotPlacement> CloneList(List<SpotPlacement> spotPlacements)
{
    foreach (SpotPlacement sp in spotPlacements)
    {
        yield return (SpotPlacement)sp.Clone();
    }
}

而在另一个地方:

public object Clone()
{
    OrderItem newOrderItem = new OrderItem();
    ...
    newOrderItem._exactPlacements.AddRange(SpotPlacement.CloneList(_exactPlacements));
    ...
    return newOrderItem;
}

我试图想出这样做的oneliner,但这是不可能的,因为yield不会在匿名方法块内工作。

更好的是,使用泛型List <T> cloner:

class Utility<T> where T : ICloneable
{
    static public IEnumerable<T> CloneList(List<T> tl)
    {
        foreach (T t in tl)
        {
            yield return (T)t.Clone();
        }
    }
}

我想要一个非常简单的对象,主要是原始类和列表的克隆。 如果你的对象是开箱即用的JSON序列化的,那么这个方法就可以做到。 这不需要修改或实现克隆类上的接口,只需要JSON.NET等JSON序列化程序。

public static T Clone<T>(T source)
{
    var serialized = JsonConvert.SerializeObject(source);
    return JsonConvert.DeserializeObject<T>(serialized);
}

按着这些次序:

  • Define an ISelf<T> with a read-only Self property that returns T , and ICloneable<out T> , which derives from ISelf<T> and includes a method T Clone() .
  • Then define a CloneBase type which implements a protected virtual generic VirtualClone casting MemberwiseClone to the passed-in type.
  • Each derived type should implement VirtualClone by calling the base clone method and then doing whatever needs to be done to properly clone those aspects of the derived type which the parent VirtualClone method hasn't yet handled.

For maximum inheritance versatility, classes exposing public cloning functionality should be sealed , but derive from a base class which is otherwise identical except for the lack of cloning. Rather than passing variables of the explicit clonable type, take a parameter of type ICloneable<theNonCloneableType> . This will allow a routine that expects a cloneable derivative of Foo to work with a cloneable derivative of DerivedFoo , but also allow the creation of non-cloneable derivatives of Foo .


最好的是实现一个扩展方法

public static T DeepClone<T>(this T originalObject)
{ /* the cloning code */ }

然后在解决方案的任何地方使用它

var copy = anyObject.DeepClone();

我们可以有以下三种实现:

  1. 通过序列化 (最短的代码)
  2. 通过反射 - 快5倍
  3. 表达式树 - 速度提高20倍

所有链接的方法工作良好,并经过深入测试。


简短的答案是你从IClo​​neable接口继承,然后实现.clone函数。 克隆应执行成员复制并对需要它的任何成员执行深层复制,然后返回结果对象。 这是一个递归操作(它要求您要克隆的类的所有成员都是值类型或实现ICloneable,并且它们的成员是值类型或实现ICloneable等等)。

有关使用ICloneable进行克隆的更多详细说明,请参阅本文

长的答案是“这取决于”。 正如其他人所提到的那样,ICloneable不被泛型支持,需要对循环类引用进行特殊考虑,并且实际上被某些人视为.NET Framework中的“错误” 。 序列化方法取决于您的对象是可序列化的,它们可能不是,您可能无法控制。 在社区中,还有很多争论是“最好的”做法。 事实上,没有一种解决方案适用于像ICloneable最初解释的那样的所有情况。

有关更多选项,请参阅此开发人员专栏文章 (称赞伊恩)。


虽然标准的做法是实现ICloneable接口( here描述,所以我不会反胃),这是一个很好的深层克隆对象复制器,我在The Code Project上找到了它,并将它合并到我们的东西中。

如别处所述,它确实需要您的对象是可序列化的。

using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;

/// <summary>
/// Reference Article http://www.codeproject.com/KB/tips/SerializedObjectCloner.aspx
/// Provides a method for performing a deep copy of an object.
/// Binary Serialization is used to perform the copy.
/// </summary>
public static class ObjectCopier
{
    /// <summary>
    /// Perform a deep Copy of the object.
    /// </summary>
    /// <typeparam name="T">The type of object being copied.</typeparam>
    /// <param name="source">The object instance to copy.</param>
    /// <returns>The copied object.</returns>
    public static T Clone<T>(T source)
    {
        if (!typeof(T).IsSerializable)
        {
            throw new ArgumentException("The type must be serializable.", "source");
        }

        // Don't serialize a null object, simply return the default for that object
        if (Object.ReferenceEquals(source, null))
        {
            return default(T);
        }

        IFormatter formatter = new BinaryFormatter();
        Stream stream = new MemoryStream();
        using (stream)
        {
            formatter.Serialize(stream, source);
            stream.Seek(0, SeekOrigin.Begin);
            return (T)formatter.Deserialize(stream);
        }
    }
}

这个想法是,它序列化你的对象,然后将它反序列化为一个新的对象。 好处是,当对象变得太复杂时,你不必关心克隆所有东西。

并使用扩展方法(也来自最初引用的来源):

如果您更喜欢使用C#3.0的新扩展方法 ,请将该方法更改为具有以下签名:

public static T Clone<T>(this T source)
{
   //...
}

现在方法调用变成了objectBeingCloned.Clone();

编辑 (2015年1月10日)以为我会重温这个,提到我最近开始使用(Newtonsoft)Json来做到这一点,它应该更轻,并避免[Serializable]标签的开销。 ( NB @atconway在评论中指出,私有成员不是使用JSON方法克隆的)

/// <summary>
/// Perform a deep Copy of the object, using Json as a serialisation method. NOTE: Private members are not cloned using this method.
/// </summary>
/// <typeparam name="T">The type of object being copied.</typeparam>
/// <param name="source">The object instance to copy.</param>
/// <returns>The copied object.</returns>
public static T CloneJson<T>(this T source)
{            
    // Don't serialize a null object, simply return the default for that object
    if (Object.ReferenceEquals(source, null))
    {
        return default(T);
    }

    // initialize inner objects individually
    // for example in default constructor some list property initialized with some values,
    // but in 'source' these items are cleaned -
    // without ObjectCreationHandling.Replace default constructor values will be added to result
    var deserializeSettings = new JsonSerializerSettings {ObjectCreationHandling = ObjectCreationHandling.Replace};

    return JsonConvert.DeserializeObject<T>(JsonConvert.SerializeObject(source), deserializeSettings);
}




clone