XmlAttributeOverrides Classe

Définition

Permet de substituer des attributs de propriété, de champ et de classe lorsque vous utilisez XmlSerializer pour sérialiser ou désérialiser un objet.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
Héritage
XmlAttributeOverrides

Exemples

L’exemple suivant sérialise une classe nommée Orchestra, qui contient un champ unique nommé Instruments qui retourne un tableau d’objets Instrument.The following example serializes a class named Orchestra, which contains a single field named Instruments that returns an array of Instrument objects. Une deuxième classe nommée Brass hérite de la classe Instrument.A second class named Brass inherits from the Instrument class. L’exemple utilise une instance de la classe XmlAttributeOverrides pour remplacer le champ Instrument, ce qui permet au champ d’accepter Brass objets.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

Remarques

La XmlAttributeOverrides permet au XmlSerializer de remplacer la méthode par défaut de sérialisation d’un jeu d’objets.The XmlAttributeOverrides enables the XmlSerializer to override the default way of serializing a set of objects. La substitution de la sérialisation de cette manière a deux utilisations : tout d’abord, vous pouvez contrôler et augmenter la sérialisation des objets trouvés dans une DLL, même si vous n’avez pas accès à la source. Deuxièmement, vous pouvez créer un ensemble de classes sérialisables, mais sérialiser les objets de plusieurs façons.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. Par exemple, au lieu de sérialiser les membres d’une instance de classe en tant qu’éléments XML, vous pouvez les sérialiser en tant qu’attributs XML, ce qui se traduit par un document plus efficace à transporter.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.

Après avoir créé un objet XmlAttributeOverrides, vous le transmettez en tant qu’argument au constructeur XmlSerializer.After you create an XmlAttributeOverrides object, you pass it as an argument to the XmlSerializer constructor. Le XmlSerializer résultant utilise les données contenues dans le XmlAttributeOverrides pour remplacer des attributs qui contrôlent la façon dont les objets sont sérialisés.The resulting XmlSerializer uses the data contained by the XmlAttributeOverrides to override attributes that control how objects are serialized. Pour ce faire, le XmlAttributeOverrides contient une collection des types d’objets qui sont substitués, ainsi qu’un objet XmlAttributes associé à chaque type d’objet substitué.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. L’objet XmlAttributes lui-même contient un ensemble approprié d’objets attribut qui contrôlent la façon dont chaque champ, propriété ou classe est sérialisé.The XmlAttributes object itself contains an appropriate set of attribute objects that control how each field, property, or class is serialized.

Le processus de création et d’utilisation d’un objet XmlAttributeOverrides est le suivant :The process for creating and using an XmlAttributeOverrides object is as follows:

  1. Créez un objet XmlAttributes.Create an XmlAttributes object.

  2. Créez un objet attribut approprié à l’objet en cours de substitution.Create an attribute object that is appropriate to the object being overridden. Par exemple, pour remplacer un champ ou une propriété, créez un XmlElementAttributeà l’aide du nouveau type dérivé.For example, to override a field or property, create an XmlElementAttribute, using the new, derived type. Vous pouvez éventuellement assigner un nouveau ElementNameou Namespace qui remplace le nom ou l’espace de noms d’attribut de la classe de base.You can optionally assign a new ElementName, or Namespace that overrides the base class's attribute name or namespace.

  3. Ajoutez l’objet attribut à la propriété ou à la collection de XmlAttributes appropriée.Add the attribute object to the appropriate XmlAttributes property or collection. Par exemple, vous ajoutez le XmlElementAttribute à la collection XmlElements de l’objet XmlAttributes, en spécifiant le nom du membre qui est substitué.For example, you would add the XmlElementAttribute to the XmlElements collection of the XmlAttributes object, specifying the member name that is being overridden.

  4. Créez un objet XmlAttributeOverrides.Create an XmlAttributeOverrides object.

  5. À l’aide de la méthode Add, ajoutez l’objet XmlAttributes à l’objet XmlAttributeOverrides.Using the Add method, add the XmlAttributes object to the XmlAttributeOverrides object. Si l’objet substitué est un XmlRootAttribute ou XmlTypeAttribute, vous devez uniquement spécifier le type de l’objet substitué.If the object being overridden is an XmlRootAttribute or XmlTypeAttribute, you need only to specify the type of the overridden object. Toutefois, si vous substituez un champ ou une propriété, vous devez également spécifier le nom du membre substitué.But if you are overriding a field or property, you must also specify the name of the overridden member.

  6. Lors de la construction du XmlSerializer, transmettez le XmlAttributeOverrides au constructeur XmlSerializer.When constructing the XmlSerializer, pass the XmlAttributeOverrides to the XmlSerializer constructor.

  7. Utilisez le XmlSerializer résultant pour sérialiser ou désérialiser les objets de classe dérivée.Use the resulting XmlSerializer to serialize or deserialize the derived class objects.

Constructeurs

XmlAttributeOverrides()

Initialise une nouvelle instance de la classe XmlAttributeOverrides.Initializes a new instance of the XmlAttributeOverrides class.

Propriétés

Item[Type, String]

Obtient l'objet associé au type spécifié de classe de base.Gets the object associated with the specified (base-class) type. Le paramètre relatif au membre indique le membre de la classe de base qui est substitué.The member parameter specifies the base-class member that is overridden.

Item[Type]

Obtient l'objet associé au type spécifié de classe de base.Gets the object associated with the specified, base-class, type.

Méthodes

Add(Type, String, XmlAttributes)

Ajoute un objet XmlAttributes à la collection d'objets XmlAttributes.Adds an XmlAttributes object to the collection of XmlAttributes objects. Le paramètre type spécifie l'objet qui sera substitué.The type parameter specifies an object to be overridden. Le paramètre member spécifie le nom du membre à substituer.The member parameter specifies the name of a member that is overridden.

Add(Type, XmlAttributes)

Ajoute un objet XmlAttributes à la collection d'objets XmlAttributes.Adds an XmlAttributes object to the collection of XmlAttributes objects. Le paramètre type spécifie l'objet auquel se substituera l'objet XmlAttributes.The type parameter specifies an object to be overridden by the XmlAttributes object.

Equals(Object)

Détermine si l'objet spécifié est égal à l'objet actuel.Determines whether the specified object is equal to the current object.

(Hérité de Object)
GetHashCode()

Sert de fonction de hachage par défaut.Serves as the default hash function.

(Hérité de Object)
GetType()

Obtient le Type de l'instance actuelle.Gets the Type of the current instance.

(Hérité de Object)
MemberwiseClone()

Crée une copie superficielle du Object actuel.Creates a shallow copy of the current Object.

(Hérité de Object)
ToString()

Retourne une chaîne qui représente l'objet en cours.Returns a string that represents the current object.

(Hérité de Object)

S’applique à

Voir aussi