Detailed explanation of how to implement copy and deep copy in C#

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The difference between deep copy and shallow copy is that shallow copy only copies the value of the value type, but the object contained in the instance still points to the original There are examples.

 class Program
  {
    [Serializable]
    public class Car 
    {
      public string name;
      public Car(string name)
      {
        this.name = name;
      }
    }
    [Serializable]
    public class Person:ICloneable
    {
      public int id;
      public string name;
      public Car car;
      public Person()
      {
      }
      public Person(int id, string name, Car car)
      {
        this.id = id;
        this.name = name;
        this.car = car;
      }

      public Object Clone() //实现ICloneable接口，达到浅表复制。浅表复制与深度复制无直接有关系。 对外提供一个创建自身的浅表副本的能力
      {
        return this.MemberwiseClone();
      }

    }

    //要复制的实例必须可序列化，包括实例引用的其它实例都必须在类定义时加[Serializable]特性。
    public static T Copy<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);
      }
    }  

   
    static void Main(string[] args)
    {
      Person p1 = new Person(1, "Scott", new Car("宝马"));
      Console.WriteLine("原始值：P1:id={0}----------->name={1}------>car={2}", p1.id, p1.name, p1.car.name);
      Person p2 = Copy<Person>(p1); //克隆一个对象
      Person p3 = p1.Clone() as Person;//浅表复制
      Console.WriteLine("改变P1的值");
      p1.id = 2;
      p1.name = "Lacy";
      p1.car.name = "红旗";
      Console.WriteLine("P1:id={0}----------->name={1}------>car={2}", p1.id, p1.name, p1.car.name);
      Console.WriteLine("深度复制：P2:id={0}----------->name={1}------>car={2}", p2.id, p2.name, p2.car.name);
      Console.WriteLine("浅表复制：P3:id={0}----------->name={1}------>car={2}", p3.id, p3.name, p3.car.name);
      Console.ReadKey();

    }

Run results:

##1. When T in the List object is a value type (int type, etc. )

For a List of value types, you can copy it directly using the following method:

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

2. T in the List object is In the case of reference types (such as custom entity classes)

1. Lists of reference types cannot be copied using the above method. Only references to objects in the List will be copied. You can use the following Extension method copy:

static class Extensions 
 { 
     public static IList<T> Clone<T>(this IList<T> listToClone) where T: ICloneable 
     { 
         return listToClone.Select(item => (T)item.Clone()).ToList(); 
     } 
 //<SPAN style="COLOR: #000000">当然前题是List中的对象要实现ICloneable接口</SPAN>
 }

2. Another method of deep copying the reference object is serialization. This method is the most reliable.

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. Using System.

Xml.Serialization to implement serialization and deserialization

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);
      }
}

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