XmlArrayItemAttribute 類別

定義

命名空間:

System.Xml.Serialization

組件:

System.Xml.XmlSerializer.dll

表示屬性，這個屬性會指定 XmlSerializer 可置於序列化陣列中的衍生型別。

public ref class XmlArrayItemAttribute : Attribute

[System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Parameter | System.AttributeTargets.Property | System.AttributeTargets.ReturnValue, AllowMultiple=true)]
public class XmlArrayItemAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Parameter | System.AttributeTargets.Property | System.AttributeTargets.ReturnValue, AllowMultiple=true)>]
type XmlArrayItemAttribute = class
    inherit Attribute

Public Class XmlArrayItemAttribute
Inherits Attribute

繼承

Object

Attribute

XmlArrayItemAttribute

屬性

AttributeUsageAttribute

範例

下列範例序列化名為 Group 的類別，其中包含名為 Employees 的 Employee 欄位，該欄位會傳回 物件的陣列。 此範例會將 XmlArrayItemAttribute 套用至 欄位，藉此指示 XmlSerializer 它可以將基類 () Employee 型別的物件和衍生類別類型 Manager () 插入序列化陣列中。

#using <System.Xml.dll>
#using <System.dll>

using namespace System;
using namespace System::IO;
using namespace System::Xml::Serialization;

public ref class Employee
{
public:
   String^ Name;
};

public ref class Manager: public Employee
{
public:
   int Level;
};

public ref class Group
{
public:

   /* The XmlArrayItemAttribute allows the XmlSerializer to insert
      both the base type (Employee) and derived type (Manager) 
      into serialized arrays. */

   [XmlArrayItem(Manager::typeid),
   XmlArrayItem(Employee::typeid)]
   array<Employee^>^Employees;

   /* Use the XmlArrayItemAttribute to specify types allowed
      in an array of Object items. */

   [XmlArray]
   [XmlArrayItem(Int32::typeid,
   ElementName="MyNumber"),
   XmlArrayItem(String::typeid,
   ElementName="MyString"),
   XmlArrayItem(Manager::typeid)]
   array<Object^>^ExtraInfo;
};

void SerializeObject( String^ filename )
{
   // Creates a new XmlSerializer.
   XmlSerializer^ s = gcnew XmlSerializer( Group::typeid );

   // Writing the XML file to disk requires a TextWriter.
   TextWriter^ writer = gcnew StreamWriter( filename );
   Group^ group = gcnew Group;
   Manager^ manager = gcnew Manager;
   Employee^ emp1 = gcnew Employee;
   Employee^ emp2 = gcnew Employee;
   manager->Name = "Consuela";
   manager->Level = 3;
   emp1->Name = "Seiko";
   emp2->Name = "Martina";
   array<Employee^>^emps = {manager,emp1,emp2};
   group->Employees = emps;

   // Creates an int and a string and assigns to ExtraInfo.
   array<Object^>^temp = {43,"Extra",manager};
   group->ExtraInfo = temp;

   // Serializes the object, and closes the StreamWriter.
   s->Serialize( writer, group );
   writer->Close();
}

void DeserializeObject( String^ filename )
{
   FileStream^ fs = gcnew FileStream( filename,FileMode::Open );
   XmlSerializer^ x = gcnew XmlSerializer( Group::typeid );
   Group^ g = dynamic_cast<Group^>(x->Deserialize( fs ));
   Console::WriteLine( "Members:" );
   System::Collections::IEnumerator^ myEnum = g->Employees->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Employee^ e = safe_cast<Employee^>(myEnum->Current);
      Console::WriteLine( "\t{0}", e->Name );
   }
}

int main()
{
   SerializeObject( "TypeDoc.xml" );
   DeserializeObject( "TypeDoc.xml" );
}

using System;
using System.IO;
using System.Xml.Serialization;

public class Group
{
   /* The XmlArrayItemAttribute allows the XmlSerializer to insert
      both the base type (Employee) and derived type (Manager)
      into serialized arrays. */

   [XmlArrayItem(typeof(Manager)),
   XmlArrayItem(typeof(Employee))]
   public Employee[] Employees;

   /* Use the XmlArrayItemAttribute to specify types allowed
      in an array of Object items. */
   [XmlArray]
   [XmlArrayItem (typeof(int),
   ElementName = "MyNumber"),
   XmlArrayItem (typeof(string),
   ElementName = "MyString"),
   XmlArrayItem(typeof(Manager))]
   public object [] ExtraInfo;
}

public class Employee
{
   public string Name;
}

public class Manager:Employee{
   public int Level;
}

public class Run
{
   public static void Main()
   {
      Run test = new Run();
      test.SerializeObject("TypeDoc.xml");
      test.DeserializeObject("TypeDoc.xml");
   }

   public void SerializeObject(string filename)
   {
      // Creates a new XmlSerializer.
      XmlSerializer s = new XmlSerializer(typeof(Group));

      // Writing the XML file to disk requires a TextWriter.
      TextWriter writer = new StreamWriter(filename);
      Group group = new Group();

      Manager manager = new Manager();
      Employee emp1 = new Employee();
      Employee emp2 = new Employee();
      manager.Name = "Consuela";
      manager.Level = 3;
      emp1.Name = "Seiko";
      emp2.Name = "Martina";
      Employee [] emps = new Employee[3]{manager, emp1, emp2};
      group.Employees = emps;

      // Creates an int and a string and assigns to ExtraInfo.
      group.ExtraInfo = new Object[3]{43, "Extra", manager};

      // Serializes the object, and closes the StreamWriter.
      s.Serialize(writer, group);
      writer.Close();
   }

   public void DeserializeObject(string filename)
   {
      FileStream fs = new FileStream(filename, FileMode.Open);
      XmlSerializer x = new XmlSerializer(typeof(Group));
      Group g = (Group) x.Deserialize(fs);
      Console.WriteLine("Members:");

      foreach(Employee e in g.Employees)
      {
         Console.WriteLine("\t" + e.Name);
      }
   }
}

Option Explicit
Option Strict

Imports System.IO
Imports System.Xml.Serialization

Public Class Group
    ' The XmlArrayItemAttribute allows the XmlSerializer to insert
    ' both the base type (Employee) and derived type (Manager)
    ' into serialized arrays. 
    
    <XmlArrayItem(GetType(Manager)), _
     XmlArrayItem(GetType(Employee))> _
    Public Employees() As Employee
    
    ' Use the XmlArrayItemAttribute to specify types allowed
    ' in an array of Object items. 
    <XmlArray(), _
     XmlArrayItem(GetType(Integer), ElementName := "MyNumber"), _
     XmlArrayItem(GetType(String), ElementName := "MyString"), _
     XmlArrayItem(GetType(Manager))> _
    Public ExtraInfo() As Object
End Class

Public Class Employee
    Public Name As String
End Class

Public Class Manager
    Inherits Employee
    Public Level As Integer
End Class


Public Class Run
    
    Public Shared Sub Main()
        Dim test As New Run()
        test.SerializeObject("TypeDoc.xml")
        test.DeserializeObject("TypeDoc.xml")
    End Sub
    
       
    Public Sub SerializeObject(ByVal filename As String)
        ' Creates a new XmlSerializer.
        Dim s As New XmlSerializer(GetType(Group))
        
        ' Writing the XML file to disk requires a TextWriter.
        Dim writer As New StreamWriter(filename)
        Dim group As New Group()
        
        Dim manager As New Manager()
        Dim emp1 As New Employee()
        Dim emp2 As New Employee()
        manager.Name = "Consuela"
        manager.Level = 3
        emp1.Name = "Seiko"
        emp2.Name = "Martina"
        Dim emps() As Employee = {manager, emp1, emp2}
        group.Employees = emps
        
        ' Creates an int and a string and assigns to ExtraInfo.
        group.ExtraInfo = New Object() {43, "Extra", manager}
        
        ' Serializes the object, and closes the StreamWriter.
        s.Serialize(writer, group)
        writer.Close()
    End Sub
    
    
    Public Sub DeserializeObject(ByVal filename As String)
        Dim fs As New FileStream(filename, FileMode.Open)
        Dim x As New XmlSerializer(GetType(Group))
        Dim g As Group = CType(x.Deserialize(fs), Group)
        Console.WriteLine("Members:")
        
        Dim e As Employee
        For Each e In  g.Employees
            Console.WriteLine(ControlChars.Tab & e.Name)
        Next e
    End Sub
End Class

備註

XmlArrayItemAttribute屬於一系列屬性，可控制序列化或還原序列化物件的方式 XmlSerializer 。 如需類似屬性的完整清單，請參閱 控制 XML 序列化的屬性。

您可以將 套用 XmlArrayItemAttribute 至任何傳回陣列的公用讀取/寫入成員，或提供對陣列的存取權。 例如，傳回 物件陣列、集合、、 ArrayList 或任何實作 介面之類別的 IEnumerable 欄位。

XmlArrayItemAttribute支援多型，換句話說，它允許 XmlSerializer 將衍生的物件新增至陣列。 例如，假設名為 Mammal 的類別衍生自名為 Animal 的基類。 此外，假設名為 MyAnimals 的類別包含傳回物件陣列的 Animal 欄位。 若要允許 XmlSerializer 同時序列化 Animal 和 Mammal 型別，請在每次指定兩個可接受的類型之一時，將 套用 XmlArrayItemAttribute 至 欄位兩次。

注意

您可以套用 或 XmlElementAttribute 的 XmlArrayItemAttribute 多個實例，以指定可以插入陣列的物件類型。

注意

不支援傳回介面或介面陣列的欄位或屬性序列化。

如需使用屬性的詳細資訊，請參閱 屬性。

注意

您可以在程式碼中使用這個字， XmlArrayItem 而不是較長 XmlArrayItemAttribute 的 。

建構函式

XmlArrayItemAttribute()	初始化 XmlArrayItemAttribute 類別的新執行個體。
XmlArrayItemAttribute(String)	初始化 XmlArrayItemAttribute 類別的新執行個體，指定 XML 文件中產生的 XML 項目名稱。
XmlArrayItemAttribute(String, Type)	初始化 XmlArrayItemAttribute 類別的新執行個體，指定 XML 文件中產生的 XML 項目名稱，以及可插入所產生之 XML 文件的 Type。
XmlArrayItemAttribute(Type)	初始化 XmlArrayItemAttribute 類別的新執行個體，指定可插入序列化陣列的 Type。

屬性

DataType	取得或設定產生的 XML 項目的 XML 資料型別。
ElementName	取得或設定產生的 XML 項目的名稱。
Form	取得或設定值，指出產生的 XML 項目名稱是否為限定的。
IsNullable	取得或設定值，指出 XmlSerializer 是否必須將成員序列化為 xsi:nil 屬性設為 true 的空 XML 標記。
Namespace	取得或設定產生的 XML 項目之的命名空間。
NestingLevel	取得或設定 XmlArrayItemAttribute 影響的 XML 項目的階層架構中的層級。
Type	取得或設定陣列中允許的型別。
TypeId	在衍生類別中實作時，取得這個 Attribute 的唯一識別碼。 (繼承來源 Attribute)

方法

Equals(Object)	傳回值，這個值指出此執行個體是否與指定的物件相等。 (繼承來源 Attribute)
GetHashCode()	傳回這個執行個體的雜湊碼。 (繼承來源 Attribute)
GetType()	取得目前執行個體的 Type。 (繼承來源 Object)
IsDefaultAttribute()	在衍生類別中覆寫時，表示這個執行個體的值是衍生類別的預設值。 (繼承來源 Attribute)
Match(Object)	在衍生類別中覆寫時，會傳回值，表示這個執行個體是否等於指定物件。 (繼承來源 Attribute)
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)

另請參閱

• XmlArrayAttribute
• XmlSerializer
• XmlArrayItems
• XmlAttributeOverrides
• XmlAttributes
• XML 序列化簡介
• HOW TO：指定 XML 資料流的替代元素名稱
• 使用屬性控制 XML 序列化
• XML 序列化的範例
• XML 架構定義工具 (Xsd.exe)