XmlAttributeOverrides 類別

定義

當使用 XmlSerializer 來序列化或還原序列化物件時,允許您覆寫屬性 (Property)、欄位和類別屬性 (Attribute)。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
繼承
XmlAttributeOverrides

範例

下列範例會序列化名為 Orchestra的類別,其中包含名為 Instruments 的單一欄位,會傳回 Instrument 物件的陣列。The following example serializes a class named Orchestra, which contains a single field named Instruments that returns an array of Instrument objects. 名為 Brass 的第二個類別會繼承自 Instrument 類別。A second class named Brass inherits from the Instrument class. 此範例會使用 XmlAttributeOverrides 類別的實例來覆寫 Instrument 欄位,讓欄位接受 Brass 物件。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

備註

XmlAttributeOverrides 可讓 XmlSerializer 覆寫序列化一組物件的預設方式。The XmlAttributeOverrides enables the XmlSerializer to override the default way of serializing a set of objects. 以這種方式覆寫序列化有兩種用法:第一,您可以控制和增強 DLL 中找到的物件序列化--即使您沒有來源的存取權也一樣。第二,您可以建立一組可序列化的類別,但以多種方式序列化物件。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. 例如,您可以將類別實例的成員序列化為 xml 屬性,而不是將其序列化,以提供更有效率的傳輸檔。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.

建立 XmlAttributeOverrides 物件之後,您會將它當做引數傳遞給 XmlSerializer 的函式。After you create an XmlAttributeOverrides object, you pass it as an argument to the XmlSerializer constructor. 產生的 XmlSerializer 會使用 XmlAttributeOverrides 所包含的資料來覆寫屬性,以控制物件的序列化方式。The resulting XmlSerializer uses the data contained by the XmlAttributeOverrides to override attributes that control how objects are serialized. 為了達成此目的,XmlAttributeOverrides 包含被覆寫的物件類型集合,以及與每個覆寫物件類型相關聯的 XmlAttributes 物件。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. XmlAttributes 物件本身包含一組適當的屬性物件,可控制每個欄位、屬性或類別的序列化方式。The XmlAttributes object itself contains an appropriate set of attribute objects that control how each field, property, or class is serialized.

建立和使用 XmlAttributeOverrides 物件的程式如下所示:The process for creating and using an XmlAttributeOverrides object is as follows:

  1. 建立 XmlAttributes 物件。Create an XmlAttributes object.

  2. 建立適用于被覆寫之物件的屬性物件。Create an attribute object that is appropriate to the object being overridden. 例如,若要覆寫欄位或屬性,請使用新的衍生型別來建立 XmlElementAttributeFor example, to override a field or property, create an XmlElementAttribute, using the new, derived type. 您可以選擇性地指派新的 ElementName,或會覆寫基類之屬性名稱或命名空間的 NamespaceYou can optionally assign a new ElementName, or Namespace that overrides the base class's attribute name or namespace.

  3. 將屬性物件加入至適當的 XmlAttributes 屬性或集合。Add the attribute object to the appropriate XmlAttributes property or collection. 例如,您會將 XmlElementAttribute 新增至 XmlAttributes 物件的 XmlElements 集合,並指定要覆寫的成員名稱。For example, you would add the XmlElementAttribute to the XmlElements collection of the XmlAttributes object, specifying the member name that is being overridden.

  4. 建立 XmlAttributeOverrides 物件。Create an XmlAttributeOverrides object.

  5. 使用 Add 方法,將 XmlAttributes 物件加入至 XmlAttributeOverrides 物件。Using the Add method, add the XmlAttributes object to the XmlAttributeOverrides object. 如果要覆寫的物件是 XmlRootAttributeXmlTypeAttribute,您只需要指定覆寫物件的類型。If the object being overridden is an XmlRootAttribute or XmlTypeAttribute, you need only to specify the type of the overridden object. 但是,如果您要覆寫欄位或屬性,您也必須指定覆寫成員的名稱。But if you are overriding a field or property, you must also specify the name of the overridden member.

  6. 在建立 XmlSerializer時,請將 XmlAttributeOverrides 傳遞至 XmlSerializer 的函式。When constructing the XmlSerializer, pass the XmlAttributeOverrides to the XmlSerializer constructor.

  7. 使用產生的 XmlSerializer,將衍生類別物件序列化或還原序列化。Use the resulting XmlSerializer to serialize or deserialize the derived class objects.

建構函式

XmlAttributeOverrides()

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

屬性

Item[Type, String]

取得與指定的 (基底類別) 型別相關的物件。Gets the object associated with the specified (base-class) type. 成員參數會指定已覆寫的基底類別成員。The member parameter specifies the base-class member that is overridden.

Item[Type]

取得與指定的、基底類別、型別相關的物件Gets the object associated with the specified, base-class, type.

方法

Add(Type, String, XmlAttributes)

XmlAttributes 物件加入 XmlAttributes 物件的集合。Adds an XmlAttributes object to the collection of XmlAttributes objects. type 參數會指定要被覆寫的物件。The type parameter specifies an object to be overridden. member 參數指定覆寫的成員名稱。The member parameter specifies the name of a member that is overridden.

Add(Type, XmlAttributes)

XmlAttributes 物件加入 XmlAttributes 物件的集合。Adds an XmlAttributes object to the collection of XmlAttributes objects. type 參數會指定要由 XmlAttributes 物件覆寫的物件。The type parameter specifies an object to be overridden by the XmlAttributes object.

Equals(Object)

判斷指定的物件是否等於目前的物件。Determines whether the specified object is equal to the current object.

(繼承來源 Object)
GetHashCode()

作為預設雜湊函數。Serves as the default hash function.

(繼承來源 Object)
GetType()

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

(繼承來源 Object)
MemberwiseClone()

建立目前 Object 的淺層複本 (Shallow Copy)。Creates a shallow copy of the current Object.

(繼承來源 Object)
ToString()

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

(繼承來源 Object)

適用於

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