[愛心連結：拯救一個25歲身患急性白血病的女孩[內有蘇州電視臺經濟頻道《天天山海經》為此錄製的節目視訊（蘇州話）]]如果一個型別，不一定是資料契約，和給定的資料契約具有很大的差異，而我們要將該型別的物件序列化成基於資料契約對應的XML。反之，對於一段給定的基於資料契約的XML，要通過反序列化生成該型別的物件，我們該如何實現這樣的場景？
比如下面定義了兩個型別Contact和Customer，其中Customer是資料契約，Contact的Sex屬性相當於Customer的Gender屬性，而Contact的FullName可以看成是Customer的FirstName和LastName的組合。現在我們要做的是將一個Contact物件序列化成基於Customer資料契約對應的結構的XML，或者對於一段基於Customer資料契約對應結構的XML，將其反序列化生成Contact物件。
1: public class Contact
2: {3: public string FullName
4: { get; set; } 5: 6: public string Sex
7: { get; set; } 8: 9: public override bool Equals(object obj)
10: {11: Contact contact = obj as Contact;
12: if (contact == null)
13: {14: return false;
15: } 16: 17: return this.FullName == contact.FullName && this.Sex == contact.Sex;
18: } 19: 20: public override int GetHashCode()
21: {22: return this.FullName.GetHashCode() ^ this.Sex.GetHashCode();
23: } 24: }1: [DataContract(Namespace = "http://www.artech.com")]
2: public class Customer
3: { 4: [DataMember(Order = 1)]5: public string FirstName
6: { get; set; } 7: 8: [DataMember(Order = 2)]9: public string LastName
10: { get; set; } 11: 12: [DataMember(Order = 3)]13: public string Gender
14: { get; set; } 15: }為實現上面的要求，要涉及WCF中一個特殊的概念：資料契約代理（DataContract Surrogate）。WCF通過一個介面System.Runtime.Serialization.IDataContractSurrogate來表示資料契約代理。IDataContractSurrogate用於實現在序列化、反序列化、資料契約的匯入和匯出過程中對物件或者型別的替換。以上面Contact和Customer為例，在正常的情況下，DataContractSerializer針對型別Customer對一個真正的Customer物件進行序列化，現在要求的是通過DataContractSerializer序列化一個Contact物件，並且要生成與Customer等效的XML，就要在序列化的過程中實現型別的替換（由Contact型別替換成Customer型別）和物件的替換（由Contact物件替換成Customer物件）。
我們先來看看IDataContractSurrogate的定義，序列化相關的方法有以下3個，如果想具體瞭解IDataContractSurrogate在資料契約匯入、匯出，以及程式碼生成方面的應用可以參考MSDN相關文件，在這裡就不多作介紹了。
- GetDataContractType：獲取進行序列化、反序列化或者資料契約匯入匯出基於的資料契約的型別，實現此方法相當於實現了型別的替換；
- GetObjectToSerialize：在序列化之前獲取序列化的物件，實現了此方法相當於為序列化實現了物件替換；
- GetDeserializedObject：當完成反序列化工作後，通過方法獲得被反序列化生成的物件，通過此方法可以用新的物件替換掉真正被反序列化生成的原物件。
1: public interface IDataContractSurrogate
2: { 3: Type GetDataContractType(Type type);4: object GetObjectToSerialize(object obj, Type targetType);
5: object GetDeserializedObject(object obj, Type targetType);
6: 7: object GetCustomDataToExport(MemberInfo memberInfo, Type dataContractType);
8: object GetCustomDataToExport(Type clrType, Type dataContractType);
9: void GetKnownCustomDataTypes(Collection<Type> customDataTypes);
10: Type GetReferencedTypeOnImport(string typeName, string typeNamespace, object customData);
11: CodeTypeDeclaration ProcessImportedType(CodeTypeDeclaration typeDeclaration, CodeCompileUnit compileUnit); 12: }現在我專門為Contact和Customer之間的轉換建立了一個自定義的DataContractSurrogate:ContractSurrogate。在GetDataContractType中，如果發現型別是Contact，則替換成Customer。在GetObjectToSerialize方法中，將用於序列化的Contact物件用Customer物件替換，而在GetDeserializedObject中則用Contact物件替換反序列化生成的Customer物件。
1: public class ContractSurrogate : IDataContractSurrogate
2: { 3: 4: public object GetCustomDataToExport(Type clrType, Type dataContractType)
5: {6: return null;
7: } 8: 9: public object GetCustomDataToExport(MemberInfo memberInfo, Type dataContractType)
10: {11: return null;
12: } 13: 14: public Type GetDataContractType(Type type)
15: {16: if (type == typeof(Contact))
17: {18: return typeof(Customer);
19: } 20: 21: return type;
22: } 23: 24: public object GetDeserializedObject(object obj, Type targetType)
25: {26: Customer customer = obj as Customer;
27: if (customer == null)
28: {29: return obj;
30: } 31: 32: return new Contact
33: {34: FullName = string.Format("{0} {1}", customer.FirstName, customer.LastName),
35: Sex = customer.Gender 36: }; 37: } 38: 39: public void GetKnownCustomDataTypes(Collection<Type> customDataTypes)
40: { 41: 42: } 43: 44: public object GetObjectToSerialize(object obj, Type targetType)
45: {46: Contact contact = obj as Contact;
47: if (contact == null)
48: {49: return obj;
50: } 51: 52: 53: return new Customer
54: {55: FirstName = contact.FullName.Split(" ".ToCharArray())[0],
56: LastName = contact.FullName.Split(" ".ToCharArray())[1],
57: Gender = contact.Sex 58: }; 59: } 60: 61: public Type GetReferencedTypeOnImport(string typeName, string typeNamespace, object customData)
62: {63: return null;
64: } 65: 66: public CodeTypeDeclaration ProcessImportedType(CodeTypeDeclaration typeDeclaration, CodeCompileUnit compileUnit)
67: {68: return typeDeclaration;
69: } 70: }為了演示ContractSurrogate在序列化和反序列化中所起的作用，建立了Serialize<T>和Deserialize<T>兩個輔助方法，通過建立DataContractSerializer進行序列化和反序列化。方法中的dataContractSurrogate引數被傳入DataContractSerializer的建構函式中。
1: public static void Serialize<T>(T instance, string fileName, IDataContractSurrogate dataContractSurrogate)
2: {3: DataContractSerializer serializer = new DataContractSerializer(typeof(T), null, int.MaxValue, false, false, dataContractSurrogate);
4: using (XmlWriter writer = new XmlTextWriter(fileName, Encoding.UTF8))
5: { 6: serializer.WriteObject(writer, instance); 7: Process.Start(fileName); 8: } 9: } 10: 11: public static T Deserialize<T>( string fileName, IDataContractSurrogate dataContractSurrogate)
12: {13: DataContractSerializer serializer = new DataContractSerializer(typeof(T), null, int.MaxValue, false, false, dataContractSurrogate);
14: using (XmlReader reader = new XmlTextReader(fileName))
15: {16: return (T)serializer.ReadObject(reader);
17: } 18: }藉助於上面定義的ContractSurrogate和兩個輔助方法，我們通過下面的程式演示IDataContractSurrogate在序列化和反序列化過程中所起的作用。
1: string fileName = @"E:\contact.xml";
2: Contact contactToSerialize = new Contact
3: {4: FullName = "Bill Gates",
5: Sex = "Male"
6: };7: IDataContractSurrogate dataContractSurrogate = new ContractSurrogate();
8: Serialize<Contact>(contactToSerialize, fileName, dataContractSurrogate); 9: 10: Contact contactToDeserialize = Deserialize<Contact>(fileName, dataContractSurrogate);11: Console.WriteLine("contactToSerialize.Equals(contactToDeserialize) = {0}", contactToSerialize.Equals(contactToDeserialize) );
下面的XML表述Contract物件被序列化後的結果，顯而易見，這和真正序列化一個Customer物件是完全一樣的。不僅如此，基於下面一段XML反序列化生成的Contact物件和用於序列化的物件是相等的，這通過最終的輸出結果可以看出來。
1: <Customer xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.artech.com">
2: <FirstName>Bill</FirstName>
3: <LastName>Gates</LastName>
4: <Gender>Male</Gender>
5: </Customer>
輸出結果：
1: contactToSerialize.Equals(contactToDeserialize) = True在進行服務寄宿的時候，可以通過如下程式碼指定IDataContractSurrogate。
1: using (ServiceHost serviceHost = new ServiceHost(typeof(InventoryCheck)))
2: foreach (ServiceEndpoint ep in serviceHost.Description.Endpoints)
3: {4: foreach (OperationDescription op in ep.Contract.Operations)
5: { 6: DataContractSerializerOperationBehavior dataContractBehavior = 7: op.Behaviors.Find<DataContractSerializerOperationBehavior>()8: as DataContractSerializerOperationBehavior;
9: if (op.Behaviors.Find<DataContractSerializerOperationBehavior>()
10: != null)
11: dataContractBehavior.DataContractSurrogate = new ContractSurrogate();
12: op.Behaviors.Add(op.Behaviors. 13: Find<DataContractSerializerOperationBehavior>()); 14: 15: dataContractBehavior = new DataContractSerializerOperationBehavior(op);
16: dataContractBehavior.DataContractSurrogate = 17: new ContractSurrogate ();
18: op.Behaviors.Add(dataContractBehavior); 19: } 20: }
注：部分內容節選自《WCF技術剖析（卷1）》第五章:序列化與資料契約（Serialization and Data Contract）
出處：http://artech.cnblogs.com
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