XmlAttributeOverrides XmlAttributeOverrides XmlAttributeOverrides XmlAttributeOverrides Class

Definição

Permite a substituição de propriedade, campo e atributos de classe quando você usa o XmlSerializer para serializar ou desserializar um objeto.Allows you to override property, field, and class attributes when you use the XmlSerializer to serialize or deserialize an object.

public ref class XmlAttributeOverrides
public class XmlAttributeOverrides
type XmlAttributeOverrides = class
Public Class XmlAttributeOverrides
Herança
XmlAttributeOverridesXmlAttributeOverridesXmlAttributeOverridesXmlAttributeOverrides

Exemplos

O exemplo a seguir serializa uma classe chamada Orchestra, que contém um único campo chamado Instruments que retorna uma matriz de Instrument objetos.The following example serializes a class named Orchestra, which contains a single field named Instruments that returns an array of Instrument objects. Uma segunda classe denominada Brass herda Instrument da classe.A second class named Brass inherits from the Instrument class. O exemplo usa uma instância da XmlAttributeOverrides classe para substituir o Instrument campo, permitindo que o campo aceite Brass objetos.The example uses an instance of the XmlAttributeOverrides class to override the Instrument field, allowing the field to accept Brass objects.

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

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

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

public ref class Brass: public Instrument
{
public:
   bool IsValved;
};

public ref class Orchestra
{
public:
   array<Instrument^>^Instruments;
};

void SerializeObject( String^ filename )
{
   /* Each overridden field, property, or type requires 
      an XmlAttributes object. */
   XmlAttributes^ attrs = gcnew XmlAttributes;

   /* Create an XmlElementAttribute to override the 
      field that returns Instrument objects. The overridden field
      returns Brass objects instead. */
   XmlElementAttribute^ attr = gcnew XmlElementAttribute;
   attr->ElementName = "Brass";
   attr->Type = Brass::typeid;

   // Add the element to the collection of elements.
   attrs->XmlElements->Add( attr );

   // Create the XmlAttributeOverrides object.
   XmlAttributeOverrides^ attrOverrides = gcnew XmlAttributeOverrides;

   /* Add the type of the class that contains the overridden 
      member and the XmlAttributes to override it with to the 
      XmlAttributeOverrides object. */
   attrOverrides->Add( Orchestra::typeid, "Instruments", attrs );

   // Create the XmlSerializer using the XmlAttributeOverrides.
   XmlSerializer^ s = gcnew XmlSerializer( Orchestra::typeid,attrOverrides );

   // Writing the file requires a TextWriter.
   TextWriter^ writer = gcnew StreamWriter( filename );

   // Create the object that will be serialized.
   Orchestra^ band = gcnew Orchestra;

   // Create an object of the derived type.
   Brass^ i = gcnew Brass;
   i->Name = "Trumpet";
   i->IsValved = true;
   array<Instrument^>^myInstruments = {i};
   band->Instruments = myInstruments;

   // Serialize the object.
   s->Serialize( writer, band );
   writer->Close();
}

void DeserializeObject( String^ filename )
{
   XmlAttributeOverrides^ attrOverrides = gcnew XmlAttributeOverrides;
   XmlAttributes^ attrs = gcnew XmlAttributes;

   // Create an XmlElementAttribute to override the Instrument.
   XmlElementAttribute^ attr = gcnew XmlElementAttribute;
   attr->ElementName = "Brass";
   attr->Type = Brass::typeid;

   // Add the XmlElementAttribute to the collection of objects.
   attrs->XmlElements->Add( attr );
   attrOverrides->Add( Orchestra::typeid, "Instruments", attrs );

   // Create the XmlSerializer using the XmlAttributeOverrides.
   XmlSerializer^ s = gcnew XmlSerializer( Orchestra::typeid,attrOverrides );
   FileStream^ fs = gcnew FileStream( filename,FileMode::Open );
   Orchestra^ band = dynamic_cast<Orchestra^>(s->Deserialize( fs ));
   Console::WriteLine( "Brass:" );

   /* The difference between deserializing the overridden 
      XML document and serializing it is this: To read the derived 
      object values, you must declare an object of the derived type 
      (Brass), and cast the Instrument instance to it. */
   Brass^ b;
   System::Collections::IEnumerator^ myEnum = band->Instruments->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      Instrument^ i = safe_cast<Instrument^>(myEnum->Current);
      b = dynamic_cast<Brass^>(i);
      Console::WriteLine( "{0}\n{1}", b->Name, b->IsValved );
   }
}

int main()
{
   SerializeObject( "Override.xml" );
   DeserializeObject( "Override.xml" );
}
using System;
using System.IO;
using System.Xml.Serialization;

public class Orchestra
{
   public Instrument[] Instruments;
}   

public class Instrument
{
   public string Name;
}

public class Brass:Instrument
{
   public bool IsValved;
}

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

    public void SerializeObject(string filename)
    {
      /* Each overridden field, property, or type requires 
      an XmlAttributes object. */
      XmlAttributes attrs = new XmlAttributes();

      /* Create an XmlElementAttribute to override the 
      field that returns Instrument objects. The overridden field
      returns Brass objects instead. */
      XmlElementAttribute attr = new XmlElementAttribute();
      attr.ElementName = "Brass";
      attr.Type = typeof(Brass);

      // Add the element to the collection of elements.
      attrs.XmlElements.Add(attr);

      // Create the XmlAttributeOverrides object.
      XmlAttributeOverrides attrOverrides = new XmlAttributeOverrides();

      /* Add the type of the class that contains the overridden 
      member and the XmlAttributes to override it with to the 
      XmlAttributeOverrides object. */
      attrOverrides.Add(typeof(Orchestra), "Instruments", attrs);

      // Create the XmlSerializer using the XmlAttributeOverrides.
      XmlSerializer s = 
      new XmlSerializer(typeof(Orchestra), attrOverrides);

      // Writing the file requires a TextWriter.
      TextWriter writer = new StreamWriter(filename);

      // Create the object that will be serialized.
      Orchestra band = new Orchestra();
      
      // Create an object of the derived type.
      Brass i = new Brass();
      i.Name = "Trumpet";
      i.IsValved = true;
      Instrument[] myInstruments = {i};
      band.Instruments = myInstruments;

      // Serialize the object.
      s.Serialize(writer,band);
      writer.Close();
   }

   public void DeserializeObject(string filename)
   {
      XmlAttributeOverrides attrOverrides = 
         new XmlAttributeOverrides();
      XmlAttributes attrs = new XmlAttributes();

      // Create an XmlElementAttribute to override the Instrument.
      XmlElementAttribute attr = new XmlElementAttribute();
      attr.ElementName = "Brass";
      attr.Type = typeof(Brass);

      // Add the XmlElementAttribute to the collection of objects.
      attrs.XmlElements.Add(attr);

      attrOverrides.Add(typeof(Orchestra), "Instruments", attrs);

      // Create the XmlSerializer using the XmlAttributeOverrides.
      XmlSerializer s = 
      new XmlSerializer(typeof(Orchestra), attrOverrides);

      FileStream fs = new FileStream(filename, FileMode.Open);
      Orchestra band = (Orchestra) s.Deserialize(fs);
      Console.WriteLine("Brass:");

      /* The difference between deserializing the overridden 
      XML document and serializing it is this: To read the derived 
      object values, you must declare an object of the derived type 
      (Brass), and cast the Instrument instance to it. */
      Brass b;
      foreach(Instrument i in band.Instruments) 
      {
         b = (Brass)i;
         Console.WriteLine(
         b.Name + "\n" + 
         b.IsValved);
      }
   }
}

Option Explicit
Option Strict

Imports System.IO
Imports System.Xml.Serialization

Public Class Orchestra
    Public Instruments() As Instrument
End Class

Public Class Instrument
    Public Name As String
End Class

Public Class Brass
    Inherits Instrument
    Public IsValved As Boolean
End Class

Public Class Run
    
    Public Shared Sub Main()
        Dim test As New Run()
        test.SerializeObject("Override.xml")
        test.DeserializeObject("Override.xml")
    End Sub
        
    Public Sub SerializeObject(ByVal filename As String)
        ' Each overridden field, property, or type requires
        ' an XmlAttributes object. 
        Dim attrs As New XmlAttributes()
        
        ' Create an XmlElementAttribute to override the
        ' field that returns Instrument objects. The overridden field
        ' returns Brass objects instead. 
        Dim attr As New XmlElementAttribute()
        attr.ElementName = "Brass"
        attr.Type = GetType(Brass)
        
        ' Add the element to the collection of elements.
        attrs.XmlElements.Add(attr)
        
        ' Create the XmlAttributeOverrides object.
        Dim attrOverrides As New XmlAttributeOverrides()
        
        ' Add the type of the class that contains the overridden
        ' member and the XmlAttributes to override it with to the
        ' XmlAttributeOverrides object. 
        attrOverrides.Add(GetType(Orchestra), "Instruments", attrs)
        
        ' Create the XmlSerializer using the XmlAttributeOverrides.
        Dim s As New XmlSerializer(GetType(Orchestra), attrOverrides)
        
        ' Writing the file requires a TextWriter.
        Dim writer As New StreamWriter(filename)
        
        ' Create the object that will be serialized.
        Dim band As New Orchestra()
        
        ' Create an object of the derived type.
        Dim i As New Brass()
        i.Name = "Trumpet"
        i.IsValved = True
        Dim myInstruments() As Instrument = {i}
        band.Instruments = myInstruments
        
        ' Serialize the object.
        s.Serialize(writer, band)
        writer.Close()
    End Sub    
    
    Public Sub DeserializeObject(filename As String)
        Dim attrOverrides As New XmlAttributeOverrides()
        Dim attrs As New XmlAttributes()
        
        ' Create an XmlElementAttribute to override the Instrument.
        Dim attr As New XmlElementAttribute()
        attr.ElementName = "Brass"
        attr.Type = GetType(Brass)
        
        ' Add the XmlElementAttribute to the collection of objects.
        attrs.XmlElements.Add(attr)
        
        attrOverrides.Add(GetType(Orchestra), "Instruments", attrs)
        
        ' Create the XmlSerializer using the XmlAttributeOverrides.
        Dim s As New XmlSerializer(GetType(Orchestra), attrOverrides)
        
        Dim fs As New FileStream(filename, FileMode.Open)
        Dim band As Orchestra = CType(s.Deserialize(fs), Orchestra)
        Console.WriteLine("Brass:")
        
        ' The difference between deserializing the overridden
        ' XML document and serializing it is this: To read the derived
        ' object values, you must declare an object of the derived type
        ' (Brass), and cast the Instrument instance to it. 
        Dim b As Brass
        Dim i As Instrument
        For Each i In  band.Instruments
            b = CType(i, Brass)
            Console.WriteLine(b.Name & ControlChars.Cr & b.IsValved)
        Next i
    End Sub
End Class

Comentários

O XmlAttributeOverrides permite que XmlSerializer o substitua a maneira padrão de serializar um conjunto de objetos.The XmlAttributeOverrides enables the XmlSerializer to override the default way of serializing a set of objects. A substituição da serialização dessa maneira tem dois usos: primeiro, você pode controlar e aumentar a serialização de objetos encontrados em uma DLL, mesmo que não tenha acesso à origem; em segundo lugar, você pode criar um conjunto de classes serializáveis, mas serializar os objetos de várias maneiras.Overriding serialization in this way has two uses: first, you can control and augment the serialization of objects found in a DLL--even if you do not have access to the source; second, you can create one set of serializable classes, but serialize the objects in multiple ways. Por exemplo, em vez de serializar membros de uma instância de classe como elementos XML, você pode serializá-los como atributos XML, resultando em um documento mais eficiente a ser transportado.For example, instead of serializing members of a class instance as XML elements, you can serialize them as XML attributes, resulting in a more efficient document to transport.

Depois de criar um XmlAttributeOverrides objeto, você o passa como um argumento para o XmlSerializer Construtor.After you create an XmlAttributeOverrides object, you pass it as an argument to the XmlSerializer constructor. O resultado XmlSerializer usa os dados contidos XmlAttributeOverrides pelo para substituir atributos que controlam como os objetos são serializados.The resulting XmlSerializer uses the data contained by the XmlAttributeOverrides to override attributes that control how objects are serialized. Para fazer isso, o XmlAttributeOverrides contém uma coleção dos tipos de objeto que são substituídos, bem como um XmlAttributes objeto associado a cada tipo de objeto substituído.To accomplish this, the XmlAttributeOverrides contains a collection of the object types that are overridden, as well as an XmlAttributes object associated with each overridden object type. O XmlAttributes objeto em si contém um conjunto apropriado de objetos de atributo que controlam como cada campo, propriedade ou classe é serializado.The XmlAttributes object itself contains an appropriate set of attribute objects that control how each field, property, or class is serialized.

O processo para criar e usar um XmlAttributeOverrides objeto é o seguinte:The process for creating and using an XmlAttributeOverrides object is as follows:

  1. Crie um XmlAttributes objeto.Create an XmlAttributes object.

  2. Crie um objeto de atributo que seja apropriado para o objeto que está sendo substituído.Create an attribute object that is appropriate to the object being overridden. Por exemplo, para substituir um campo ou propriedade, crie um XmlElementAttribute, usando o novo tipo derivado.For example, to override a field or property, create an XmlElementAttribute, using the new, derived type. Opcionalmente, você pode atribuir um ElementNamenovo ou Namespace que substitua o namespace ou nome de atributo da classe base.You can optionally assign a new ElementName, or Namespace that overrides the base class's attribute name or namespace.

  3. Adicione o objeto de atributo à propriedade XmlAttributes ou coleção apropriada.Add the attribute object to the appropriate XmlAttributes property or collection. Por exemplo, você adicionaria a XmlElementAttribute XmlElements à coleção do XmlAttributes objeto, especificando o nome do membro que está sendo substituído.For example, you would add the XmlElementAttribute to the XmlElements collection of the XmlAttributes object, specifying the member name that is being overridden.

  4. Crie um XmlAttributeOverrides objeto.Create an XmlAttributeOverrides object.

  5. Usando o Add método, adicione o XmlAttributes objeto ao XmlAttributeOverrides objeto.Using the Add method, add the XmlAttributes object to the XmlAttributeOverrides object. Se o objeto que está sendo substituído XmlRootAttribute for XmlTypeAttributeum ou, você precisará apenas especificar o tipo do objeto substituído.If the object being overridden is an XmlRootAttribute or XmlTypeAttribute, you need only to specify the type of the overridden object. Mas se você estiver substituindo um campo ou propriedade, também deverá especificar o nome do membro substituído.But if you are overriding a field or property, you must also specify the name of the overridden member.

  6. Ao construir o XmlSerializer, passe o XmlAttributeOverrides para o XmlSerializer Construtor.When constructing the XmlSerializer, pass the XmlAttributeOverrides to the XmlSerializer constructor.

  7. Use o que XmlSerializer resulta em serializar ou desserializar os objetos da classe derivada.Use the resulting XmlSerializer to serialize or deserialize the derived class objects.

Construtores

XmlAttributeOverrides() XmlAttributeOverrides() XmlAttributeOverrides() XmlAttributeOverrides()

Inicializa uma nova instância da classe XmlAttributeOverrides.Initializes a new instance of the XmlAttributeOverrides class.

Propriedades

Item[Type, String] Item[Type, String] Item[Type, String] Item[Type, String]

Obtém o objeto associado ao tipo especificado (classe base).Gets the object associated with the specified (base-class) type. O parâmetro de membro especifica o membro da classe base que é substituído.The member parameter specifies the base-class member that is overridden.

Item[Type] Item[Type] Item[Type] Item[Type]

Obtém o objeto associado ao tipo de classe base especificado.Gets the object associated with the specified, base-class, type.

Métodos

Add(Type, String, XmlAttributes) Add(Type, String, XmlAttributes) Add(Type, String, XmlAttributes) Add(Type, String, XmlAttributes)

Adiciona um objeto XmlAttributes à coleção de objetos XmlAttributes.Adds an XmlAttributes object to the collection of XmlAttributes objects. O parâmetro type especifica um objeto a ser substituído.The type parameter specifies an object to be overridden. O parâmetro member especifica o nome de um membro que é substituído.The member parameter specifies the name of a member that is overridden.

Add(Type, XmlAttributes) Add(Type, XmlAttributes) Add(Type, XmlAttributes) Add(Type, XmlAttributes)

Adiciona um objeto XmlAttributes à coleção de objetos XmlAttributes.Adds an XmlAttributes object to the collection of XmlAttributes objects. O parâmetro type especifica um objeto a ser substituído pelo objeto XmlAttributes.The type parameter specifies an object to be overridden by the XmlAttributes object.

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Determina se o objeto especificado é igual ao objeto atual.Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Serve como a função de hash padrão.Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Obtém o Type da instância atual.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Cria uma cópia superficial do Object atual.Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

Retorna uma cadeia de caracteres que representa o objeto atual.Returns a string that represents the current object.

(Inherited from Object)

Aplica-se a

Veja também