WCF 第六章 序列化和编码 使用代理序列化类型

有时你可能需要完成一个不可序列化或者需要对序列化内容进行改变的序列化过程。一个例子是由第三方组件提供者提供或者一个你不再拥有源码的组件中的 一个类型。下面的例子显示了一个不可序列化的类(查看列表6.26)，Employee.这个类故意不生成一个默认构造函数而且它没有任何可写的字段或属 性。这意味着它不可使用任何我们到目前为止提到的序列化技术来序列化它。为了序列化这个类我们需要提供一个可以代表序列化类的代理。

列表6.26 不可序列化的Employee类

01	public class Employee

02

{

03	private int employeeID;

04	private string firstName;

05	private string lastName;

06

07	public Employee(int employeeID, string firstName, string lastName)

08

{

09	this.employeeID = employeeID;

10	this.firstName = firstName;

11	this.lastName = lastName;

12

}

13

14	public int EmployeeID

15

{

16	get { return employeeID; }

17

}

18

19	public string FirstName

20

{

21	get { return firstName; }

22

}

23

24	public string LastName

25

{

26	get { return lastName; }

27

}

28

}

  你需要两步来开发一个代理。第一步是定义代表序列化类型的数据契约。第二部是实现一个基于IDataContractSurrogate接口的数据契约代 理。我们将要检查三个主要的方法是GetDataContractType, GetDeserializedObject和GetObjectToSerialize方法。GetDataContractType 给DataContractSerializer返回序列化类型，GetDeserializedObject和 GetObjectToSerialize按要求执行反序列化和序列化。EmployeeSurrogate类在列表6.27中显示。

列表6.27 Employee代理类

001	using System.Runtime.Serialization;

002

003	namespace Services

004

{

005	[DataContract]

006	internal class EmployeeSurrogated

007

{

008	[DataMember]

009	private int employeeID;

010	[DataMember]

011	private string firstName;

012	[DataMember]

013	private string lastName;

014

015	public EmployeeSurrogated(int employeeID, string firstName, string lastName)

016

{

017	this.employeeID = employeeID;

018	this.firstName = firstName;

019	this.lastName = lastName;

020

}

021

022	public int EmployeeID

023

{

024	get { return employeeID; }

025

}

026

027	public string FirstName

028

{

029	get { return firstName; }

030

}

031

032	public string LastName

033

{

034	get { return lastName; }

035

}

036

}

037

038	public class EmployeeSurrogate : IDataContractSurrogate

039

{

040	#region IDataContractSurrogate Members

041

042	public object GetCustomDataToExport(Type clrType, Type dataContractType)

043

{

044	return null; //NotImplement

045

}

046

047	public object GetCustomDataToExport(System.Reflection.MemberInfo memberInfo, Type dataContractType)

048

{

049	return null; //NotImplement

050

}

051

052	public Type GetDataContractType(Type type)

053

{

054	if (typeof(Employee).IsAssignableFrom(type))

055

{

056	return typeof(EmployeeSurrogated);

057

}

058	return type;

059

}

060

061	public object GetDeserializedObject(object obj, Type targetType)

062

{

063	if (obj is EmployeeSurrogated)

064

{

065	EmployeeSurrogated oldEmployee = (EmployeeSurrogated)obj;

066	Employee newEmployee = new Employee(oldEmployee.EmployeeID, oldEmployee.FirstName, oldEmployee.LastName);

067	return newEmployee;

068

}

069	return obj;

070

}

071

072	public void GetKnownCustomDataTypes(System.Collections.ObjectModel.Collection customDataTypes)

073

{

074	throw new NotImplementedException();

075

}

076

077	public object GetObjectToSerialize(object obj, Type targetType)

078

{

079	if (obj is Employee)

080

{

081	Employee oldEmployee = (Employee)obj;

082	EmployeeSurrogated newEmployee = new EmployeeSurrogated(oldEmployee.EmployeeID, oldEmployee.FirstName, oldEmployee.LastName);

083	return newEmployee;

084

}

085	return obj;

086

}

087

088	public Type GetReferencedTypeOnImport(string typeName, string typeNamespace, object customData)

089

{

090	if (typeNamespace.Equals("http://schemas.datacontract.org/2004/07/EmployeeSurrogated"))

091

{

092	if (typeName.Equals("EmployeeSurrogated"))

093

{

094	return typeof(Employee);

095

}

096

}

097	return null;

098

}

099

100	public System.CodeDom.CodeTypeDeclaration ProcessImportedType(System.CodeDom.CodeTypeDeclaration typeDeclaration, System.CodeDom.CodeCompileUnit compileUnit)

101

{

102	return typeDeclaration;

103

}

104

105	#endregion

106

}

107

}

  我们通过让DataContractSerializer知道代理类来将所有内容放到一起。你需要实例化DataContractSerializer并将EmployeeSurrogated类传递给构造函数，如列表6.28显示。

列表6.28 使用DataContractSerializer的Employee代理类

01	class Program

02

{

03	static void TryToSerialize(Employee e)

04

{

05	DataContractSerializer dcs = new DataContractSerializer(typeof(Employee));

06	using (StringWriter sw = new StringWriter())

07

{

08	using (XmlWriter xw = XmlWriter.Create(sw))

09

{

10

try

11

{

12	dcs.WriteObject(xw, e);

13

}

14	catch(InvalidDataContractException ex)

15

{

16	Console.WriteLine("Cannot serialize without a surrogate! {0}", ex.Message);

17

}

18

}

19

}

20

}

21

22	static string SerializeUsingSurrogate(DataContractSerializer dcs, Employee e)

23

{

24	using (StringWriter sw = new StringWriter())

25

{

26	using (XmlWriter xw = XmlWriter.Create(sw))

27

{

28	dcs.WriteObject(xw, e);

29	xw.Flush();

30	return sw.ToString();

31

}

32

}

33

}

34

35	static Employee DeserializeUsingSurrogate(DataContractSerializer dcs, string employeeAsString)

36

{

37	using (StringReader tr = new StringReader(employeeAsString))

38

{

39	using (XmlReader xr = XmlReader.Create(tr))

40

{

41	return dcs.ReadObject(xr) as Employee;

42

}

43

}

44

}

45

46	static void Main(string[] args)

47

{

48	Employee e = new Employee(12345, "Daniel", "Dong");

49

50	TryToSerialize(e);

51

52	DataContractSerializer dcs = new DataContractSerializer(typeof(Employee),

53	null, int.MaxValue, false, false, new EmployeeSurrogate());

54

55	string employeeAsString = SerializeUsingSurrogate(dcs, e);

56

57	e = DeserializeUsingSurrogate(dcs, employeeAsString);

58

59	Console.ReadLine();

60

}

61

}

=======
转载自
作者：DanielWise
出处：http://www.cnblogs.com/danielWise/

 

转载于:https://www.cnblogs.com/llbofchina/archive/2011/06/30/2094159.html