C#中List<T>对象的深度拷贝问题 （Clone）

一、List<T>对象中的T是值类型的情况（int 类型等）

对于值类型的List直接用以下方法就可以复制：

List<T> oldList =new List<T>();
oldList.Add(..);

List<T> newList =new List<T>(oldList);

List<T> oldList = new List<T>();
oldList.Add(..);
List<T> newList = new List<T>(oldList);

二、List<T>对象中的T是引用类型的情况（例如自定义的实体类）

1、对于引用类型的List无法用以上方法进行复制，只会复制List中对象的引用，可以用以下扩展方法复制：

staticclass Extensions
{
publicstatic IList<T> Clone<T>(this IList<T> listToClone)
where T: ICloneable
{
return listToClone.Select(item => (T)item.Clone()).ToList();
}
//<span style="color: rgb(0, 0, 0);">当然前题是List中的对象要实现ICloneable接口</span>
}

static class Extensions
{
public static IList<T> Clone<T>(this IList<T> listToClone) where T: ICloneable
{
return listToClone.Select(item => (T)item.Clone()).ToList();
}
//当然前题是List中的对象要实现ICloneable接口
}

2、另一种用序列化的方式对引用对象完成深拷贝，此种方法最可靠

publicstatic T Clone<T>(T RealObject)

{

using (Stream objectStream = new MemoryStream())
{

//利用 System.Runtime.Serialization序列化与反序列化完成引用对象的复制
IFormatter formatter =new BinaryFormatter();
formatter.Serialize(objectStream, RealObject);
objectStream.Seek(0, SeekOrigin.Begin);
return (T)formatter.Deserialize(objectStream);
}

}

public static T Clone<T>(T RealObject)

{
using (Stream objectStream = new MemoryStream())
{
//利用 System.Runtime.Serialization序列化与反序列化完成引用对象的复制
IFormatter formatter = new BinaryFormatter();
formatter.Serialize(objectStream, RealObject);
objectStream.Seek(0, SeekOrigin.Begin);
return (T)formatter.Deserialize(objectStream);
}
}

3、利用System.Xml.Serialization来实现序列化与反序列化

publicstatic T Clone<T>(T RealObject)
{
using(Stream stream=new MemoryStream())
{

XmlSerializer serializer =new XmlSerializer(typeof(T));
serializer.Serialize(stream, RealObject);
stream.Seek(0, SeekOrigin.Begin);
return (T)serializer.Deserialize(stream);
}
}

public static T Clone<T>(T RealObject)
{
using(Stream stream=new MemoryStream())
{
XmlSerializer serializer = new XmlSerializer(typeof(T));
serializer.Serialize(stream, RealObject);
stream.Seek(0, SeekOrigin.Begin);
return (T)serializer.Deserialize(stream);
}
}

三、对上述几种对象深拷贝进行测试

测试如下:
using System;
using System.Collections.Generic;
using System.Collections ;
using System.Linq;
using System.Text;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;

namespace LINQ
{
[Serializable]

public class tt
{

private string name =
"";

public string Name

{
get {return name; }
set { name = value; }
}
privatestring sex ="";

publicstring Sex
{
get {return sex; }
set { sex = value; }
}
}

class LINQTest
{

public static T Clone<T>(T RealObject)
{
using (Stream objectStream =new MemoryStream())
{
IFormatter formatter =new BinaryFormatter();
formatter.Serialize(objectStream, RealObject);
objectStream.Seek(0, SeekOrigin.Begin);
return (T)formatter.Deserialize(objectStream);
}

}

public static void Main()
{
List<tt> lsttt =new List<tt>();
tt tt1 =new tt();
tt1.Name ="a1";
tt1.Sex ="20";
lsttt.Add(tt1);
List<tt> str=new List<tt>();
str.Add(Clone<tt>(lsttt[0]));
str[0].Name ="lv";
}
}

}