淺談C#中的深拷貝(DeepCopy)與淺拷貝(MemberwiseClone)

場景：MVVM模式中數據雙向綁定，想實現編輯、保存、撤銷操作時也雙向綁定了，不能實現撤銷操作。

后來通過搜索找到了繼承IEditableObject接口實現撤銷操作，但是對其中使用了MemberwiseClone還不是很了解。

 

MemberwiseClone：

https://msdn.microsoft.com/zh-cn/library/system.object.memberwiseclone(v=vs.110).aspx

MemberwiseClone方法創建的新對象，然后將當前對象的非靜態字段復制到新的對象創建的淺表副本。 

如果字段是值類型，則執行字段的按位復制。 

如果字段是引用類型，引用將復制，但被引用的對象不會被復制。因此，原始對象和其克隆引用同一對象。

筆記：修改克隆對象會影響原對象的引用類型。

 

DeepCopy：

In a deep copy, all objects are duplicated; in a shallow copy, only the top-level objects are duplicated and the lower levels contain references.

在深拷貝中，會復制所有對象。在淺拷貝中，僅對頂級對象進行了復制，對低級別對象進行了引用。

筆記：深拷貝中，修改克隆對象不會影響原對象。

 

附上代碼，其中Persona類實現了淺拷貝和深拷貝的方法。

深拷貝額外復制了其中自定義的類IdInfo。

using System;

public class IdInfo
{
    public int IdNumber;

    public IdInfo(int IdNumber)
    {
        this.IdNumber = IdNumber;
    }
}

public class Person 
{
    public int Age;
    public string Name;
    public IdInfo IdInfo;

    public Person ShallowCopy()
    {
       return (Person) this.MemberwiseClone();
    }

    public Person DeepCopy()
    {
       Person other = (Person) this.MemberwiseClone();
       other.IdInfo = new IdInfo(IdInfo.IdNumber);
       other.Name = String.Copy(Name);
       return other;
    }
}

public class Example
{
    public static void Main()
    {
        // Create an instance of Person and assign values to its fields.
        Person p1 = new Person();
        p1.Age = 42;
        p1.Name = "Sam";
        p1.IdInfo = new IdInfo(6565);

        // Perform a shallow copy of p1 and assign it to p2.
        Person p2 = p1.ShallowCopy();

        // Display values of p1, p2
        Console.WriteLine("Original values of p1 and p2:");
        Console.WriteLine("   p1 instance values: ");
        DisplayValues(p1);
        Console.WriteLine("   p2 instance values:");
        DisplayValues(p2);

        // Change the value of p1 properties and display the values of p1 and p2.
        p1.Age = 32;
        p1.Name = "Frank";
        p1.IdInfo.IdNumber = 7878;
        Console.WriteLine("\nValues of p1 and p2 after changes to p1:");
        Console.WriteLine("   p1 instance values: ");
        DisplayValues(p1);
        Console.WriteLine("   p2 instance values:");
        DisplayValues(p2);

        // Make a deep copy of p1 and assign it to p3.
        Person p3 = p1.DeepCopy();
        // Change the members of the p1 class to new values to show the deep copy.
        p1.Name = "George";
        p1.Age = 39;
        p1.IdInfo.IdNumber = 8641;
        Console.WriteLine("\nValues of p1 and p3 after changes to p1:");
        Console.WriteLine("   p1 instance values: ");
        DisplayValues(p1);
        Console.WriteLine("   p3 instance values:");
        DisplayValues(p3);
    }

    public static void DisplayValues(Person p)
    {
        Console.WriteLine("      Name: {0:s}, Age: {1:d}", p.Name, p.Age);
        Console.WriteLine("      Value: {0:d}", p.IdInfo.IdNumber);
    }
}