C#中List对象的深度拷贝问题

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]
    publicclass tt
    {
        privatestring name = "";

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

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

    class LINQTest
    {
        publicstatic 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);
            }
        }


        publicstaticvoid Main()
        {
            List<tt> lsttt = new List<tt>();
            tt tt1 = new tt();
            tt1.Name = "a1";
            tt1.Sex = "20";
            lsttt.Add(tt1);
            List<tt> l333 = new List<tt>();
            l333.Add(Clone<tt>(lsttt[0]));
            l333[0].Name = "333333333";
      }
  }
}