XmlArrayItemAttribute Class

Definition

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。Represents an attribute that specifies the derived types that the XmlSerializer can place in a serialized array.

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
type XmlArrayItemAttribute = class
    inherit Attribute
Public Class XmlArrayItemAttribute
Inherits Attribute
Inheritance
XmlArrayItemAttribute
Attributes

Examples

下列範例會將名為 Group 的類別序列化,其中包含一個名為 Employees 的欄位,其會傳回 Employee 物件的陣列。The following example serializes a class named Group that contains a field named Employees that returns an array of Employee objects. 這個範例會將 XmlArrayItemAttribute 套用至欄位,藉此指示 XmlSerializer 可以將基類(Employee)型別和衍生類別型別(Manager)的物件插入序列化陣列中。The example applies the XmlArrayItemAttribute to the field, thereby instructing the XmlSerializer that it can insert objects of both the base class (Employee) type and derived class type (Manager) into the serialized array.

#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

Remarks

XmlArrayItemAttribute 屬於控制 XmlSerializer 如何將物件序列化或還原序列化的一系列屬性。The XmlArrayItemAttribute belongs to a family of attributes that controls how the XmlSerializer serializes or deserializes an object. 如需類似屬性的完整清單,請參閱控制 XML 序列化的屬性For a complete list of similar attributes, see Attributes That Control XML Serialization.

您可以將 XmlArrayItemAttribute 套用至任何會傳回陣列的公用讀取/寫入成員,或提供存取權給它。You can apply the XmlArrayItemAttribute to any public read/write member that returns an array, or provides access to one. 例如,傳回物件陣列的欄位、集合、ArrayList,或任何可執行 IEnumerable 介面的類別。For example, a field that returns an array of objects, a collection, an ArrayList, or any class that implements the IEnumerable interface.

XmlArrayItemAttribute 支援多型--換句話說,它可讓 XmlSerializer 將衍生的物件加入至陣列。The XmlArrayItemAttribute supports polymorphism--in other words, it allows the XmlSerializer to add derived objects to an array. 例如,假設名為 Mammal 的類別衍生自名為 Animal的基類。For example, suppose a class named Mammal is derived from a base class named Animal. 此外,假設名為 MyAnimals 的類別包含一個會傳回 Animal 物件陣列的欄位。Further suppose that a class named MyAnimals contains a field that returns an array of Animal objects. 若要讓 XmlSerializer 同時序列化 AnimalMammal 類型,請將 XmlArrayItemAttribute 套用至欄位兩次,每次指定兩個可接受的類型之一。To allow the XmlSerializer to serialize both the Animal and Mammal type, apply the XmlArrayItemAttribute to the field twice, each time specifying one of the two acceptable types.

Note

您可以套用 XmlArrayItemAttributeXmlElementAttribute 的多個實例,以指定可插入陣列中的物件類型。You can apply multiple instances of the XmlArrayItemAttribute or XmlElementAttribute to specify types of objects that can be inserted into the array.

Note

不支援會傳回介面或介面陣列之欄位或屬性的序列化。The serialization of a field or property that returns an interface or array of interfaces is not supported.

如需使用屬性的詳細資訊,請參閱屬性For more information about using attributes, see Attributes.

Note

您可以使用程式碼中的文字 XmlArrayItem,而不是較長的 XmlArrayItemAttributeYou can use the word XmlArrayItem in your code instead of the longer XmlArrayItemAttribute.

Constructors

XmlArrayItemAttribute()

初始化 XmlArrayItemAttribute 類別的新執行個體。Initializes a new instance of the XmlArrayItemAttribute class.

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。Initializes a new instance of the XmlArrayItemAttribute class and specifies the name of the XML element generated in the XML document.

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 TypeInitializes a new instance of the XmlArrayItemAttribute class and specifies the name of the XML element generated in the XML document and the Type that can be inserted into the generated XML document.

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 TypeInitializes a new instance of the XmlArrayItemAttribute class and specifies the Type that can be inserted into the serialized array.

Properties

DataType

取得或設定產生的 XML 項目的 XML 資料型別。Gets or sets the XML data type of the generated XML element.

ElementName

取得或設定產生的 XML 項目的名稱。Gets or sets the name of the generated XML element.

Form

取得或設定值,指出產生的 XML 項目名稱是否為限定的。Gets or sets a value that indicates whether the name of the generated XML element is qualified.

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。Gets or sets a value that indicates whether the XmlSerializer must serialize a member as an empty XML tag with the xsi:nil attribute set to true.

Namespace

取得或設定產生的 XML 項目之的命名空間。Gets or sets the namespace of the generated XML element.

NestingLevel

取得或設定 XmlArrayItemAttribute 影響的 XML 項目的階層架構中的層級。Gets or sets the level in a hierarchy of XML elements that the XmlArrayItemAttribute affects.

Type

取得或設定陣列中允許的型別。Gets or sets the type allowed in an array.

TypeId

在衍生類別中實作時,取得這個 Attribute 的唯一識別碼。When implemented in a derived class, gets a unique identifier for this Attribute.

(Inherited from Attribute)

Methods

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。Returns a value that indicates whether this instance is equal to a specified object.

(Inherited from Attribute)
GetHashCode()

傳回此執行個體的雜湊碼。Returns the hash code for this instance.

(Inherited from Attribute)
GetType()

取得目前執行個體的 TypeGets the Type of the current instance.

(Inherited from 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。When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.

(Inherited from 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。When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.

(Inherited from Attribute)
MemberwiseClone()

建立目前 Object 的淺層複製。Creates a shallow copy of the current Object.

(Inherited from Object)
ToString()

傳回代表目前物件的字串。Returns a string that represents the current object.

(Inherited from Object)

Explicit Interface Implementations

_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

將一組名稱對應至一組對應的分派識別項 (Dispatch Identifier)。Maps a set of names to a corresponding set of dispatch identifiers.

(Inherited from Attribute)
_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

擷取物件的類型資訊,可以用來取得介面的類型資訊。Retrieves the type information for an object, which can be used to get the type information for an interface.

(Inherited from Attribute)
_Attribute.GetTypeInfoCount(UInt32)

擷取物件提供的類型資訊介面數目 (0 或 1)。Retrieves the number of type information interfaces that an object provides (either 0 or 1).

(Inherited from Attribute)
_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

提供物件所公開的屬性和方法的存取權。Provides access to properties and methods exposed by an object.

(Inherited from Attribute)

Applies to

See also