[C#.NET] 利用序列化進行類別深複製
續上篇，[.NET] 淺複製與深複製，我們瞭解到為什麼要進行複製，在上篇深複製是用 hard code 一行一行的賦予屬性，這會容易造成出錯，我依上篇的例子再修改一下類別以方便說明
類別群如下
[Serializable]
public class Name
{
public Name(string firstName, string lastName)
{
this.FirstName = firstName;
this.LastName = lastName;
}
public string FirstName { get; set; }
public string LastName { get; set; }
}
[Serializable]
public class CellPhone
{
private string _FullCellPhone;
public string CountryCode { get; set; }
public string Phone { get; set; }
public string FullCellPhone
{
get
{
this._FullCellPhone = this.CountryCode + this.Phone;
return this._FullCellPhone;
}
internal set { this._FullCellPhone = value; }
}
}
而Person類別的淺複製與深複製你可能會像我一樣這樣寫：
public class Person
{
public int Age { get; set; }
public string Address { get; set; }
public Name Name { get; set; }
public List<CellPhone> Phones { get; set; } = new List<CellPhone>();
public Person Clone()
{
return this.MemberwiseClone() as Person;
}
public Person DeepClone()
{
var person = new Person();
person.Age = this.Age;
person.Address = this.Address;
person.Name = this.Name;
List<CellPhone> phones = new List<CellPhone>();
foreach (var item in this.Phones)
{
phones.Add(item);
}
return person;
}
}
淺複製就不探討，我們來觀察DeepClone方法的寫法，這樣的寫法就是我剛講的hard code寫法，這樣的寫法沒有錯，方法無錯並非優，我們思考一下將會引發什麼問題：
- 屬性太多了，不小心漏打了幾個屬性，引發後續Debug的困難
- 類別成員屬性有異動時，都要再重新檢查一遍成員有無漏掉。
這是一個很糟的問題，我們該怎麼辦?
為了可以比人家早點下班，修改一下DeepClone方法，使用序列化複製一份新的執行個體。
你可以跟我這樣做：
public Person DeepClone()
{
using (var memory = new MemoryStream())
{
IFormatter formatter = new BinaryFormatter();
formatter.Serialize(memory, this);
memory.Seek(0, SeekOrigin.Begin);
return formatter.Deserialize(memory) as Person;
}
}
PS.這是一個很常見的方式，透過BinaryFormatter 將 object 轉成Stream/Byte[]
參考：
http://www.digitalcoding.com/Code-Snippets/C-Sharp/C-Code-Snippet-Object-to-byte-array.html
http://blog.csdn.net/showsunrise/article/details/4913808
來証明一下是否真的有創建一份新的執行個體
[TestMethod]
public void DeepCloneTest()
{
var target = new Person
{
Age = 18,
Address = "地球村",
Name = new Name("余", "小章"),
Phones =
new List<CellPhone>
{
new CellPhone {CountryCode = "+886", Phone = "12312121212"},
new CellPhone {CountryCode = "+886", Phone = "1232434"},
new CellPhone {CountryCode = "+886", Phone = "34535123243124"}
}
};
Person expected = null;
Person actual = target.DeepClone();
actual.Phones[0].Phone = "";
Assert.AreNotEqual(target.Phones[0].Phone, actual.Phones[0].Phone);
}觀察Phone屬性，兩個的值不一樣，確定他們兩個是不同的執行個體。
你也可以增加一個擴充方法，讓大夥都享有這樣的深複製的功能
public static class Extensions
{
public static T DeepClone<T>(this T item)
{
if (item != null)
{
using (var stream = new MemoryStream())
{
var formatter = new BinaryFormatter();
formatter.Serialize(stream, item);
stream.Seek(0, SeekOrigin.Begin);
var result = (T) formatter.Deserialize(stream);
return result;
}
}
return default(T);
}
}測試程式碼
[TestMethod]
public void DeepCloneTest()
{
var expected = new Person
{
Age = 18,
Address = "地球村",
Name = new Name("余", "小章"),
Phones =
new List<CellPhone>
{
new CellPhone {CountryCode = "+886", Phone = "12312121212"},
new CellPhone {CountryCode = "+886", Phone = "1232434"},
new CellPhone {CountryCode = "+886", Phone = "34535123243124"}
}
};
Person actual = expected.DeepClone();
actual.Phones[0].Phone = "";
Assert.AreNotEqual(expected.Phones[0].Phone, actual.Phones[0].Phone);
}
若有謬誤，煩請告知，新手發帖請多包涵
Microsoft MVP Award 2010~2017 C# 第四季
Microsoft MVP Award 2018~2022 .NET
