C#中List对象的深度拷贝问题

一、List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 oldList = new List();
 oldList.Add(..);
 List newList = new List(oldList);

二、List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：

 static class Extensions
  {
          public static IList Clone(this IList 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

 public static T Clone(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

 public static T Clone(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; }
         }
         private string sex = "";

         public string Sex
         {
             get { return sex; }
             set { sex = value; }
         }
     }

     class LINQTest
     {
         public static T Clone(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 lsttt = new List();