ExtensionDataObject 類別
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
儲存已建立版本之資料合約的資料，此資料合約已因加入新成員而得到擴充。
public ref class ExtensionDataObject sealedpublic sealed class ExtensionDataObjecttype ExtensionDataObject = classPublic NotInheritable Class ExtensionDataObject- 繼承
-
ExtensionDataObject
範例
下列程式碼範例會序列化型別 (PersonVersion2) 的執行個體，這個型別是可序列化型別 (Person) 的第二個版本。 第二個版本包含第一個版本沒有呈現的額外資料 (ID 欄位)。 接著，這段程式碼會將 XML 文件還原序列化為 Person 物件，然後立即重新序列化此包含額外資料的物件。 最後，這段程式碼會將新的 XML 還原序列化為 PersonVersion2 物件，然後將完整資料寫入至主控台，以證明資料已完成從舊版型別開始與結束的來回流程。 請注意，DataContractAttribute 屬性必須套用 Name，並且 Namespace 屬性已設定為與原始類別相同的名稱和命名空間。
using System;
using System.Xml;
using System.Runtime.Serialization;
using System.IO;
// Implement the IExtensibleDataObject interface
// to store the extra data for future versions.
[DataContract(
Name = "Person",
Namespace = "http://www.cohowinery.com/employees")]
class Person : IExtensibleDataObject
{
// To implement the IExtensibleDataObject interface,
// you must implement the ExtensionData property. The property
// holds data from future versions of the class for backward
// compatibility.
private ExtensionDataObject extensionDataObject_value;
public ExtensionDataObject ExtensionData
{
get
{
return extensionDataObject_value;
}
set
{
extensionDataObject_value = value;
}
}
[DataMember]
public string Name;
}
// The second version of the class adds a new field. The field's
// data is stored in the ExtensionDataObject field of
// the first version (Person). You must also set the Name property
// of the DataContractAttribute to match the first version.
// If necessary, also set the Namespace property so that the
// name of the contracts is the same.
[DataContract(Name = "Person",
Namespace = "http://www.cohowinery.com/employees")]
class PersonVersion2 : IExtensibleDataObject
{
// Best practice: add an Order number to new members.
[DataMember(Order=2)]
public int ID;
[DataMember]
public string Name;
private ExtensionDataObject extensionDataObject_value;
public ExtensionDataObject ExtensionData
{
get
{
return extensionDataObject_value;
}
set
{
extensionDataObject_value = value;
}
}
}
public sealed class Program
{
private Program()
{
// Private constructor to prevent creation of this class.
}
public static void Main()
{
try
{
WriteVersion2("V2.xml");
WriteToVersion1("v2.xml");
ReadVersion2("v2.xml");
}
catch (SerializationException exc)
{
Console.WriteLine("{0}: {1}", exc.Message, exc.StackTrace);
}
finally
{
Console.ReadLine();
}
}
// Create an instance of the version 2.0 class. It has
// extra data (ID field) that version 1.0 does
// not understand.
static void WriteVersion2(string path)
{
Console.WriteLine("Creating a version 2 object");
PersonVersion2 p2 = new PersonVersion2();
p2.Name = "Elizabeth";
p2.ID = 2006;
Console.WriteLine("Object data includes an ID");
Console.WriteLine("\t Name: {0}", p2.Name);
Console.WriteLine("\t ID: {0} \n", p2.ID);
// Create an instance of the DataContractSerializer.
DataContractSerializer ser =
new DataContractSerializer(typeof(PersonVersion2));
Console.WriteLine("Serializing the v2 object to a file. \n\n");
FileStream fs = new FileStream(path, FileMode.Create);
ser.WriteObject(fs, p2);
fs.Close();
}
// Deserialize version 2 data to a version 1 object.
static void WriteToVersion1(string path)
{
// Create the serializer using the version 1 type.
DataContractSerializer ser =
new DataContractSerializer(typeof(Person));
FileStream fs = new FileStream(path, FileMode.Open);
XmlDictionaryReader reader =
XmlDictionaryReader.CreateTextReader(fs, new XmlDictionaryReaderQuotas());
Console.WriteLine
("Deserializing v2 data to v1 object. \n\n");
Person p1 = (Person)ser.ReadObject(reader, false);
Console.WriteLine("V1 data has only a Name field.");
Console.WriteLine("But the v2 data is stored in the ");
Console.WriteLine("ExtensionData property. \n\n");
Console.WriteLine("\t Name: {0} \n", p1.Name);
fs.Close();
// Change data in the object.
p1.Name = "John";
Console.WriteLine("Changed the Name value to 'John' ");
Console.Write("and reserializing the object to version 2 \n\n");
// Reserialize the object.
fs = new FileStream(path, FileMode.Create);
ser.WriteObject(fs, p1);
fs.Close();
}
// Deserialize a version 2.0 object.
public static void ReadVersion2(string path)
{
FileStream fs = new FileStream(path, FileMode.Open);
DataContractSerializer ser = new DataContractSerializer(typeof(PersonVersion2));
Console.WriteLine("Deserializing new data to version 2 \n\n");
PersonVersion2 p2 = (PersonVersion2)ser.ReadObject(fs);
fs.Close();
Console.WriteLine("The data includes the old ID field value. \n");
Console.WriteLine("\t (New) Name: {0}", p2.Name);
Console.WriteLine("\t ID: {0} \n", p2.ID);
}
}
' Implement the IExtensibleDataObject interface
' to store the extra data for future versions.
<DataContract(Name := "Person", [Namespace] := "http://www.cohowinery.com/employees")> _
Class Person
Implements IExtensibleDataObject
' To implement the IExtensibleDataObject interface,
' you must implement the ExtensionData property. The property
' holds data from future versions of the class for backward
' compatibility.
Private extensionDataObject_value As ExtensionDataObject
Public Property ExtensionData() As ExtensionDataObject _
Implements IExtensibleDataObject.ExtensionData
Get
Return extensionDataObject_value
End Get
Set
extensionDataObject_value = value
End Set
End Property
<DataMember()> _
Public Name As String
End Class
' The second version of the class adds a new field. The field's
' data is stored in the ExtensionDataObject field of
' the first version (Person). You must also set the Name property
' of the DataContractAttribute to match the first version.
' If necessary, also set the Namespace property so that the
' name of the contracts is the same.
<DataContract(Name := "Person", [Namespace] := "http://www.cohowinery.com/employees")> _
Class PersonVersion2
Implements IExtensibleDataObject
' Best practice: add an Order number to new members.
<DataMember(Order:=2)> _
Public ID As Integer
<DataMember()> _
Public Name As String
Private extensionDataObject_value As ExtensionDataObject
Public Property ExtensionData() As ExtensionDataObject _
Implements IExtensibleDataObject.ExtensionData
Get
Return extensionDataObject_value
End Get
Set
extensionDataObject_value = value
End Set
End Property
End Class
NotInheritable Public Class Program
' Private constructor to prevent creation of this class.
Private Sub New()
End Sub
Public Shared Sub Main()
Try
WriteVersion2("V2.xml")
WriteToVersion1("v2.xml")
ReadVersion2("v2.xml")
Catch exc As SerializationException
Console.WriteLine("{0}: {1}", exc.Message, exc.StackTrace)
Finally
Console.ReadLine()
End Try
End Sub
' Create an instance of the version 2.0 class. It has
' extra data (ID field) that version 1.0 does
' not understand.
Shared Sub WriteVersion2(ByVal path As String)
Console.WriteLine("Creating a version 2 object")
Dim p2 As New PersonVersion2()
p2.Name = "Elizabeth"
p2.ID = 2006
Console.WriteLine("Object data includes an ID")
Console.WriteLine(vbTab + " Name: {0}", p2.Name)
Console.WriteLine(vbTab + " ID: {0} " + vbLf, p2.ID)
' Create an instance of the DataContractSerializer.
Dim ser As New DataContractSerializer(GetType(PersonVersion2))
Console.WriteLine("Serializing the v2 object to a file. " + vbLf + vbLf)
Dim fs As New FileStream(path, FileMode.Create)
ser.WriteObject(fs, p2)
fs.Close()
End Sub
' Deserialize version 2 data to a version 1 object.
Shared Sub WriteToVersion1(ByVal path As String)
' Create the serializer using the version 1 type.
Dim ser As New DataContractSerializer(GetType(Person))
Dim fs As New FileStream(path, FileMode.Open)
Dim reader As XmlDictionaryReader = _
XmlDictionaryReader.CreateTextReader(fs, New XmlDictionaryReaderQuotas())
Console.WriteLine("Deserializing v2 data to v1 object. " + vbLf + vbLf)
Dim p1 As Person = CType(ser.ReadObject(reader, False), Person)
Console.WriteLine("V1 data has only a Name field.")
Console.WriteLine("But the v2 data is stored in the ")
Console.WriteLine("ExtensionData property. " + vbLf + vbLf)
Console.WriteLine(vbTab + " Name: {0} " + vbLf, p1.Name)
reader.Close()
fs.Close()
' Change data in the object.
p1.Name = "John"
Console.WriteLine("Changed the Name value to 'John' ")
Console.Write("and reserializing the object to version 2 " + vbLf + vbLf)
' Reserialize the object.
fs = New FileStream(path, FileMode.Create)
ser.WriteObject(fs, p1)
fs.Close()
End Sub
' Deserialize a version 2.0 object.
Public Shared Sub ReadVersion2(ByVal path As String)
Dim fs As New FileStream(path, FileMode.Open)
Dim ser As New DataContractSerializer(GetType(PersonVersion2))
Console.WriteLine("Deserializing new data to version 2 " + vbLf + vbLf)
Dim p2 As PersonVersion2 = CType(ser.ReadObject(fs), PersonVersion2)
fs.Close()
Console.WriteLine("The data includes the old ID field value. " + vbLf)
Console.WriteLine(vbTab + " (New) Name: {0}", p2.Name)
Console.WriteLine(vbTab + " ID: {0} " + vbLf, p2.ID)
End Sub
End Class
備註
ExtensionDataObject 是一種結構，它會儲存 XmlObjectSerializer 在還原序列化 (Deserialization) 作業期間所遇到的額外資料。 序列化 (Serialization) 會使用這個結構將額外資料寫入至已序列化的執行個體。 ExtensionData 執行個體的 IExtensibleDataObject 屬性會傳回這個結構。
方法
| Equals(Object) |
判斷指定的物件是否等於目前的物件。 (繼承來源 Object) |
| GetHashCode() |
做為預設雜湊函式。 (繼承來源 Object) |
| GetType() |
取得目前執行個體的 Type。 (繼承來源 Object) |
| MemberwiseClone() |
建立目前 Object 的淺層複製。 (繼承來源 Object) |
| ToString() |
傳回代表目前物件的字串。 (繼承來源 Object) |
