Type: System.Xml.Serialization.XmlArrayItemAttribute

System.Xml.Serialization.XmlArrayItemAttribute Class

Assembly: System.Xml.dll
Namespace: System.Xml.Serialization

Summary: Specifies the derived types that the XmlSerializer can place in a serialized array.

C# Syntax:

[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.ReturnValue)]
public class XmlArrayItemAttribute : Attribute

Remarks

The XmlArrayItemAttribute belongs to a family of attributes that controls how the XmlSerializer serializes, or deserializes, an object. For a complete list of similar attributes, see the conceptual topic at MSDN: attributesthatcontrolserialization.

You can apply the XmlArrayItemAttribute to any public read/write member that returns an array, or provides access to one (for example, a field that returns an array of objects, a collection, an ArrayList, or any class that implements the IEnumerable interface).

The XmlArrayItemAttribute supports polymorphism--in other words, it allows the XmlSerializer to add derived objects to an array. For example, suppose a class named Mammal is derived from a base class named Animal. Further suppose that a class named MyAnimals contains a field that returns an array of Animal objects. 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 You can apply multiple instances of the XmlArrayItemAttribute or XmlElementAttribute to specify types of objects that can be inserted into the array.

Note The serialization of a field or property that returns an interface or array of interfaces is not supported.

For more information about using attributes, see the conceptual topic at MSDN: extendingmetadatausingattributes.

Note In your code, you can use the word XmlArrayItem instead of the longer XmlArrayItemAttribute.

Example

The following example serializes a class named


            Group

, which contains a field named


            Employees

that returns an array of


            Employee

objects. 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;
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)
   {
      // Create a new XmlSerializer instance.
      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;

      // Create an int and a string and assign to ExtraInfo.
      group.ExtraInfo = new Object[3]{43, "Extra", manager};

      // Serialize the object, and close 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);
      }
   }
}

System.Xml.Serialization.XmlArrayItemAttribute Member List:

Public Constructors

ctor #1	Overloaded: `.ctor()`Default constructor. This constructor is called by derived class constructors to initialize state in this type. Initializes a new instance of the XmlArrayItemAttribute class.
ctor #2	Overloaded: `.ctor(string elementName)` Initializes a new instance of the XmlArrayItemAttribute class; specifies the name of the XML element generated in the XML document.
ctor #3	Overloaded: `.ctor(Type type)` Initializes a new instance of the XmlArrayItemAttribute class; specifies the Type that can be inserted into the serialized array.
ctor #4	Overloaded: `.ctor(string elementName, Type type)` Initializes a new instance of the XmlArrayItemAttribute class; specifies the name of the XML element generated in the XML document, and the Type that can be inserted into the generated XML document.

Public Properties

DataType	Read-write Gets or sets the XML data type of the generated XML element.
ElementName	Read-write Gets or sets the name of the generated XML element.
Form	Read-write Gets or sets a value indicating whether the name of the generated XML element is qualified.
IsNullable	Read-write Gets or sets a value indicating whether the XmlSerializer should serialize a member as an empty XML tag with the xsi:nil attribute set to true.
Namespace	Read-write Gets or sets the namespace of the generated XML element.
NestingLevel	Read-write Gets or sets the level in a hierarchy of XML elements that the XmlArrayItemAttribute affects.
Type	Read-write Gets or sets the type allowed in an array.
TypeId (inherited from System.Attribute)	Read-only See base class member description: System.Attribute.TypeId When implemented in a derived class, gets a unique identifier for this Attribute.

Public Methods

Equals (inherited from System.Object)	See base class member description: System.Object.Equals Derived from System.Object, the primary base class for all objects.
GetHashCode (inherited from System.Attribute)	See base class member description: System.Attribute.GetHashCode Returns the hash code for this instance.
GetType (inherited from System.Object)	See base class member description: System.Object.GetType Derived from System.Object, the primary base class for all objects.
IsDefaultAttribute (inherited from System.Attribute)	See base class member description: System.Attribute.IsDefaultAttribute When overridden in a derived class, returns an indication whether the value of this instance is the default value for the derived class.
Match (inherited from System.Attribute)	See base class member description: System.Attribute.Match When overridden in a derived class, returns a value indicating whether this instance equals a specified object.
ToString (inherited from System.Object)	See base class member description: System.Object.ToString Derived from System.Object, the primary base class for all objects.

Protected Methods

Finalize (inherited from System.Object)	See base class member description: System.Object.Finalize Derived from System.Object, the primary base class for all objects.
MemberwiseClone (inherited from System.Object)	See base class member description: System.Object.MemberwiseClone Derived from System.Object, the primary base class for all objects.

Hierarchy:

System.Object

System.Attribute

System.Xml.Serialization.XmlArrayItemAttribute

System.Xml.Serialization.XmlArrayItemAttribute Member Details

Overloaded ctor #1

Summary: Initializes a new instance of the XmlArrayItemAttribute class.

Default constructor. This constructor is called by derived class constructors to initialize state in this type.

C# Syntax:


            public XmlArrayItemAttribute();

Example

The following serializes a class named


                Transportation

which contains a field named


                MyVehicles

that returns an array of


                Vehicle

objects. The example applies the XmlArrayItemAttribute to the field, allowing the XmlSerializer to insert instances of the

Car

class, which is derived from the


                Vehicle

class, into the array.

using System;
using System.IO;
using System.Xml;
using System.Xml.Serialization;
 
public class Vehicle
{
   public string id;
}
public class Car:Vehicle
{
   public string Maker;   
}
 
public class Transportation
{  
   [XmlArrayItem(), 
   XmlArrayItem(typeof(Car), ElementName = "Automobile")]
   public Vehicle[] MyVehicles;
}
 
public class Run
{
   public static void Main()
   {
      Run test = new Run();
      test.SerializeObject("XmlArrayItem1.xml");
      test.DeserializeObject("XmlArrayItem1.xml");
   }

   private void SerializeObject(string filename){
      // Create an XmlSerializer for the Transportation class. 
      XmlSerializer MySerializer = new XmlSerializer(typeof(Transportation));
   
      // Writing the XML file to disk requires a TextWriter.
      TextWriter myTextWriter = new StreamWriter(filename);

      // Create the object to serialize.
      Transportation myTransportation = new Transportation();

      // Create objects to add to the array.
      Vehicle myVehicle= new Vehicle() ;
      myVehicle.id = "A12345";

      Car myCar = new Car();
      myCar.id = "Car 34";
      myCar.Maker = "FamousCarMaker";

      myTransportation.MyVehicles = 
      new Vehicle[2] {myVehicle, myCar};
      
      // Serialize the object, and close the StreamWriter.
      MySerializer.Serialize(myTextWriter, myTransportation);
      myTextWriter.Close();
   }
 
   private void DeserializeObject(string filename)
   {
      // Create an XmlSerializer instance.
      XmlSerializer mySerializer = new XmlSerializer(typeof(Transportation));
      FileStream myFileStream = new FileStream(filename,FileMode.Open);
      Transportation myTransportation =
      (Transportation) mySerializer.Deserialize(myFileStream);
 
      for(int i = 0; i < myTransportation.MyVehicles.Length;i++)
      {
         Console.WriteLine(myTransportation.MyVehicles[i].id);
      }
   }
 }

XSD data type	.NET data type
anyURI	String
base64Binary	Array of Byte objects
boolean	Boolean
byte	SByte
date	DateTime
dateTime	DateTime
decimal	Decimal
double	Double
ENTITY	String
ENTITIES	String
float	Single
gDay	String
gMonth	String
gMonthDay	String
gYear	String
gYearMonth	String
hexBinary	Array of Byte objects
ID	String
IDREF	String
IDREFS	String
int	Int32
integer	String
language	String
long	Int64
Name	String
NCName	String
negativeInteger	String
NMTOKEN	String
NMTOKENS	String
normalizedString	String
nonNegativeInteger	String
nonPositiveInteger	String
NOTATION	String
positiveInteger	String
QName	XmlQualifiedName
recurringDate	String
duration	String
string	String
short	Int16
time	DateTime
token	String
unsignedByte	Byte
unsignedInt	UInt32
unsignedLong	UInt64
unsignedShort	UInt16