XmlArrayItemAttribute Class

 

Represents an attribute that specifies the derived types that the XmlSerializer can place in a serialized array.

Namespace:   System.Xml.Serialization
Assembly:  System.Xml (in System.Xml.dll)

System.Object
  System.Attribute
    System.Xml.Serialization.XmlArrayItemAttribute

<AttributeUsageAttribute(AttributeTargets.Property Or AttributeTargets.Field Or AttributeTargets.Parameter Or AttributeTargets.ReturnValue,
	AllowMultiple := True)>
Public Class XmlArrayItemAttribute
	Inherits Attribute

NameDescription
System_CAPS_pubmethodXmlArrayItemAttribute()

Initializes a new instance of the XmlArrayItemAttribute class.

System_CAPS_pubmethodXmlArrayItemAttribute(String)

Initializes a new instance of the XmlArrayItemAttribute class and specifies the name of the XML element generated in the XML document.

System_CAPS_pubmethodXmlArrayItemAttribute(String, Type)

Initializes a new instance of the XmlArrayItemAttribute class and specifies the name of the XML element generated in the XML document and the Type that can be inserted into the generated XML document.

System_CAPS_pubmethodXmlArrayItemAttribute(Type)

Initializes a new instance of the XmlArrayItemAttribute class and specifies the Type that can be inserted into the serialized array.

NameDescription
System_CAPS_pubpropertyDataType

Gets or sets the XML data type of the generated XML element.

System_CAPS_pubpropertyElementName

Gets or sets the name of the generated XML element.

System_CAPS_pubpropertyForm

Gets or sets a value that indicates whether the name of the generated XML element is qualified.

System_CAPS_pubpropertyIsNullable

Gets or sets a value that indicates whether the XmlSerializer must serialize a member as an empty XML tag with the xsi:nil attribute set to true.

System_CAPS_pubpropertyNamespace

Gets or sets the namespace of the generated XML element.

System_CAPS_pubpropertyNestingLevel

Gets or sets the level in a hierarchy of XML elements that the XmlArrayItemAttribute affects.

System_CAPS_pubpropertyType

Gets or sets the type allowed in an array.

System_CAPS_pubpropertyTypeId

When implemented in a derived class, gets a unique identifier for this Attribute.(Inherited from Attribute.)

NameDescription
System_CAPS_pubmethodEquals(Object)

This API supports the product infrastructure and is not intended to be used directly from your code. Returns a value that indicates whether this instance is equal to a specified object.(Inherited from Attribute.)

System_CAPS_protmethodFinalize()

Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)

System_CAPS_pubmethodGetHashCode()

Returns the hash code for this instance.(Inherited from Attribute.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodIsDefaultAttribute()

When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)

System_CAPS_pubmethodMatch(Object)

When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)

System_CAPS_protmethodMemberwiseClone()

Creates a shallow copy of the current Object.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

NameDescription
System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)

Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetTypeInfoCount(UInt32)

Retrieves the number of type information interfaces that an object provides (either 0 or 1).(Inherited from Attribute.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

Provides access to properties and methods exposed by an object.(Inherited from Attribute.)

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 Attributes That Control XML Serialization.

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.

System_CAPS_noteNote

You can apply multiple instances of the XmlArrayItemAttribute or XmlElementAttribute to specify types of objects that can be inserted into the array.

System_CAPS_noteNote

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 Extending Metadata Using Attributes.

System_CAPS_noteNote

You can use the word XmlArrayItem in your code instead of the longer XmlArrayItemAttribute.

The following example serializes a class named Group that 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.

Option Explicit
Option Strict

Imports System
Imports System.IO
Imports System.Xml.Serialization
Imports Microsoft.VisualBasic


Public Class Group
    ' The XmlArrayItemAttribute allows the XmlSerializer to insert
    ' both the base type (Employee) and derived type (Manager)
    ' into serialized arrays. 

    <XmlArrayItem(GetType(Manager)), _
     XmlArrayItem(GetType(Employee))> _
    Public Employees() As Employee

    ' Use the XmlArrayItemAttribute to specify types allowed
    ' in an array of Object items. 
    <XmlArray(), _
     XmlArrayItem(GetType(Integer), ElementName := "MyNumber"), _
     XmlArrayItem(GetType(String), ElementName := "MyString"), _
     XmlArrayItem(GetType(Manager))> _
    Public ExtraInfo() As Object
End Class

Public Class Employee
    Public Name As String
End Class

Public Class Manager
    Inherits Employee
    Public Level As Integer
End Class


Public Class Run

    Public Shared Sub Main()
        Dim test As New Run()
        test.SerializeObject("TypeDoc.xml")
        test.DeserializeObject("TypeDoc.xml")
    End Sub


    Public Sub SerializeObject(ByVal filename As String)
        ' Creates a new XmlSerializer.
        Dim s As New XmlSerializer(GetType(Group))

        ' Writing the XML file to disk requires a TextWriter.
        Dim writer As New StreamWriter(filename)
        Dim group As New Group()

        Dim manager As New Manager()
        Dim emp1 As New Employee()
        Dim emp2 As New Employee()
        manager.Name = "Consuela"
        manager.Level = 3
        emp1.Name = "Seiko"
        emp2.Name = "Martina"
        Dim emps() As Employee = {manager, emp1, emp2}
        group.Employees = emps

        ' Creates an int and a string and assigns to ExtraInfo.
        group.ExtraInfo = New Object() {43, "Extra", manager}

        ' Serializes the object, and closes the StreamWriter.
        s.Serialize(writer, group)
        writer.Close()
    End Sub


    Public Sub DeserializeObject(ByVal filename As String)
        Dim fs As New FileStream(filename, FileMode.Open)
        Dim x As New XmlSerializer(GetType(Group))
        Dim g As Group = CType(x.Deserialize(fs), Group)
        Console.WriteLine("Members:")

        Dim e As Employee
        For Each e In  g.Employees
            Console.WriteLine(ControlChars.Tab & e.Name)
        Next e
    End Sub
End Class

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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