C#中List對象的深度拷貝問題 （Clone）

一、List<T>對象中的T是值類型的情況（int 類型等）

對於值類型的List直接用以下方法就可以複製：

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>對象中的T是引用類型的情況（例如自定義的實體類）

1、對於引用類型的List無法用以上方法進行復制，只會複製List中對象的引用，可以用以下擴展方法複製：

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);">當然前題是List中的對象要實現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(); 
         } 
 //當然前題是List中的對象要實現ICloneable接口
 } 

2、另一種用序列化的方式對引用對象完成深拷貝，此種方法最可靠

publicstatic T Clone<T>(T RealObject)

{
     
using (Stream objectStream = new MemoryStream())
     {
           //利用 System.Runtime.Serialization序列化與反序列化完成引用對象的複製
             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序列化與反序列化完成引用對象的複製
             IFormatter formatter = new BinaryFormatter(); 
             formatter.Serialize(objectStream, RealObject); 
             objectStream.Seek(0, SeekOrigin.Begin); 
             return (T)formatter.Deserialize(objectStream); 
     } 
} 

3、利用System.Xml.Serialization來實現序列化與反序列化

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、對上述幾種對象深拷貝進行測試

 

測試如下:
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";
      }
  }
}