學藝不精，陸續踩了幾次雷，整理DataContract與DataMember對序列化的影響備忘。
WCF預設使用DataContractSerializer執行序列化，而DataContractSerializer可依物件類別標註的[DataContract]及[DataMember]、[IgnoreDataMember]等Attribute決定哪些屬性該序列化。依照MSDN文件，DataContractSerializer的處理原則為：
- 類別標示[DataContract]時，只序列化有標示[DataMember]的項目
註：DataMember不限於public Property，可用於各種存取層級（public、private、internal、protected）的Property或Field。 - 若類別未標示[DataContract]，DataContractSerializer預設會序列化「所有可讀寫的public Property及Field」，此時可透過[IgnoreDataMember]負向表列不要序列化的Property或Field。
我設計了以下幾個型別來觀察DataContractSerializer行為，有Property有Field，有public有private，再配合[DataContract]、[DataMember]、[IgnoreDataMember]組合出不同變化：
using System.Runtime.Serialization;[DataContract]
publicclass Blah1
{publicint PropNoAttr { get; set; }
publicint Field;
privateint PrivProp { get; set; }
privateint PrivField;
}
[DataContract]
publicclass Blah2
{publicint PropNoAttr { get; set; }
[DataMember]
publicint PropAttr { get; set; }
publicint Field;
[DataMember]
privateint PrivProp { get; set; }
[DataMember]
privateint PrivField;
}
[DataContract]
publicclass Blah3
{publicint PropNoAttr { get; set; }
[IgnoreDataMember]
publicint PropIgnoreAttr { get; set; }
publicint Field;
privateint PrivProp { get; set; }
privateint PrivField;
}
publicclass Blah4
{publicint PropNoAttr { get; set; }
[DataMember]
publicint PropAttr { get; set; }
[IgnoreDataMember]
publicint PropIgnoreAttr { get; set; }
publicint Field;
privateint PrivProp { get; set; }
privateint PrivField;
}
publicclass Blah5
{publicint PropNoAttr { get; set; }
publicint ReadonlyProp { get; }
publicint Field;
privateint PrivProp { get; set; }
privateint PrivField;
}
測試程式很簡單，用DataContractSerializer將Blah1到Blah5序列化成XML，Console.WriteLine出來，借用XDocument將XML以縮排格式輸出。
using System;using System.IO;using System.Runtime.Serialization;using System.Text;using System.Xml.Linq;namespace ConsoleApplication1{class Program {staticvoid Main(string[] args)
{ Console.WriteLine(Serialize<Blah1>(new Blah1())); Console.WriteLine(Serialize<Blah2>(new Blah2())); Console.WriteLine(Serialize<Blah3>(new Blah3())); Console.WriteLine(Serialize<Blah4>(new Blah4())); Console.WriteLine(Serialize<Blah5>(new Blah5()));Console.Read();
}
staticstring Serialize<T>(T graph)
{DataContractSerializer dcs = new DataContractSerializer(typeof(T));
MemoryStream ms = new MemoryStream();dcs.WriteObject(ms, graph);
XDocument xd = XDocument.Parse(Encoding.UTF8.GetString(ms.ToArray()));
returntypeof(T).ToString() +"\n=====================================\n" + xd.ToString() + "\n";}
}
}
執行結果如下：
Blah1
=====================================
<Blah1xmlns="http://schemas.datacontract.org/2004/07/"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance"/>
Blah2
=====================================
<Blah2xmlns="http://schemas.datacontract.org/2004/07/"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
<PrivField>0</PrivField>
<PrivProp>0</PrivProp>
<PropAttr>0</PropAttr>
</Blah2>
Blah3
=====================================
<Blah3xmlns="http://schemas.datacontract.org/2004/07/"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance"/>
Blah4
=====================================
<Blah4xmlns="http://schemas.datacontract.org/2004/07/"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
<Field>0</Field>
<PropAttr>0</PropAttr>
<PropNoAttr>0</PropNoAttr>
</Blah4>
Blah5
=====================================
<Blah5xmlns="http://schemas.datacontract.org/2004/07/"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
<Field>0</Field>
<PropNoAttr>0</PropNoAttr>
</Blah5>
- Blah1
只標了[DataContract]沒標任何[DataMember]，XML空空如也，沒有任何Property或Field被序列化 - Blah2
標註[DataContract]後，所有標註[DataMember]的成員都包含在XML中，不論public或private，不管是Property或是Field - Blah3
標註[DataContract]後DataContractSerializer只認[DataMember]辦事，[IgnoreDataMember]沒有作用，XML是空的 - Blah4
未標註[DataContract]，除了[IgnoreDataMember] PropIgnoreAttr外，所有public的Property及Field都被序列化 - Blah4
未加任何Attribute，DataContractSerializer將序列化所有公開Property及Field，但Property限定可讀寫者，刻意放了一個public ReadonlyProp { get; }唯讀屬性，果然被排除了。
實驗驗證完畢！