XmlAttributeOverrides Class
Allows you to override property, field, and class attributes when you use the XmlSerializer to serialize or deserialize an object.
Assembly: System.Xml (in System.Xml.dll)
The XmlAttributeOverrides type exposes the following members.
| Name | Description | |
|---|---|---|
![]() ![]() ![]() | XmlAttributeOverrides | Initializes a new instance of the XmlAttributeOverrides class. |
| Name | Description | |
|---|---|---|
![]() ![]() ![]() | Item[Type] | Gets the object associated with the specified, base-class, type. |
![]() ![]() ![]() | Item[Type, String] | Gets the object associated with the specified (base-class) type. The member parameter specifies the base-class member that is overridden. |
| Name | Description | |
|---|---|---|
![]() ![]() ![]() | Add(Type, XmlAttributes) | Adds an XmlAttributes object to the collection of XmlAttributes objects. The type parameter specifies an object to be overridden by the XmlAttributes object. |
![]() ![]() ![]() | Add(Type, String, XmlAttributes) | Adds an XmlAttributes object to the collection of XmlAttributes objects. The type parameter specifies an object to be overridden. The member parameter specifies the name of a member that is overridden. |
![]() ![]() ![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() ![]() ![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() ![]() ![]() | GetHashCode | Serves as a hash function for a particular type. (Inherited from Object.) |
![]() ![]() ![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() ![]() ![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() ![]() ![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
The XmlAttributeOverrides enables the XmlSerializer to override the default way of serializing a set of objects. 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. 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.
After you create an XmlAttributeOverrides object, you pass it as an argument to the XmlSerializer constructor. The resulting XmlSerializer uses the data contained by the XmlAttributeOverrides to override attributes that control how objects are serialized. 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. The XmlAttributes object itself contains an appropriate set of attribute objects that control how each field, property, or class is serialized.
The process for creating and using an XmlAttributeOverrides object is as follows:
Create an XmlAttributes object.
Create an attribute object that is appropriate to the object being overridden. For example, to override a field or property, create an XmlElementAttribute, using the new, derived type. You can optionally assign a new ElementName, or Namespace that overrides the base class's attribute name or namespace.
Add the attribute object to the appropriate XmlAttributes property or collection. For example, you would add the XmlElementAttribute to the XmlElements collection of the XmlAttributes object, specifying the member name that is being overridden.
Create an XmlAttributeOverrides object.
Using the Add method, add the XmlAttributes object to the XmlAttributeOverrides object. If the object being overridden is an XmlRootAttribute or XmlTypeAttribute, you need only to specify the type of the overridden object. But if you are overriding a field or property, you must also specify the name of the overridden member.
When constructing the XmlSerializer, pass the XmlAttributeOverrides to the XmlSerializer constructor.
Use the resulting XmlSerializer to serialize or deserialize the derived class objects.
The following example serializes a class named Orchestra, which contains a single field named Instruments that returns an array of Instrument objects. A second class named Brass inherits from the Instrument class. 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" ); }
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

