DataMemberAttribute Class

Definition

Namespace:

System.Runtime.Serialization

Assembly:

System.Runtime.Serialization.Primitives.dll

Source:

DataMemberAttribute.cs

When applied to the member of a type, specifies that the member is part of a data contract and is serializable by the DataContractSerializer.

public ref class DataMemberAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple=false, Inherited=false)]
public sealed class DataMemberAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Field | System.AttributeTargets.Property, AllowMultiple=false, Inherited=false)>]
type DataMemberAttribute = class
    inherit Attribute

Public NotInheritable Class DataMemberAttribute
Inherits Attribute

Inheritance

Object

Attribute

DataMemberAttribute

Attributes

AttributeUsageAttribute

Examples

The following example shows a type to which the DataContractAttribute and DataMemberAttribute attributes have been applied. The Name property on the DataMemberAttribute is set to "ID".

using System;
using System.Collections;
using System.IO;
using System.Runtime.Serialization;
using System.Xml;

// You must apply a DataContractAttribute or SerializableAttribute
// to a class to have it serialized by the DataContractSerializer.
[DataContract()]
class Person : IExtensibleDataObject
{
    private string LastNameValue;
    // Apply the DataMemberAttribute to fields (or properties)
    // that must be serialized.
    [DataMember()]
    public string FirstName;

    [DataMember]
    public string LastName
    {
        get { return LastNameValue; }
        set { LastNameValue = value; }
    }

    [DataMember(Name = "ID")]
    public int IdNumber;

    // Note that you can apply the DataMemberAttribute to
    // a private field as well.
    [DataMember]
    private string Secret;

    public Person(string newfName, string newLName, int newIdNumber)
    {
        FirstName = newfName;
        LastName = newLName;
        IdNumber = newIdNumber;
        Secret = newfName + newLName + newIdNumber;
    }

    // The extensionDataValue field holds data from future versions
    // of the type.  This enables this type to be compatible with
    // future versions. The field is required to implement the
    // IExtensibleDataObject interface.

    private ExtensionDataObject extensionDatavalue;

    public ExtensionDataObject ExtensionData
    {
        get
        {
            return extensionDatavalue;
        }
        set
        {
            extensionDatavalue = value;
        }
    }
}

public class Test
{
    public static void Main(string[] args)
    {
        try
        {
            WriteObject(@"DataMemberAttributeExample.xml");
            ReadObject(@"DataMemberAttributeExample.xml");
        }
        catch (Exception exc)
        {
            Console.WriteLine(
            "The serialization operation failed: {0} StackTrace: {1}",
            exc.Message, exc.StackTrace);
        }
        finally
        {
            Console.WriteLine("Press <Enter> to exit....");
            Console.ReadLine();
        }
    }

    public static void WriteObject(string filename)
    {
        // Create a new instance of the Person class.
        Person p1 = new Person("Zighetti", "Barbara", 101);
        FileStream writer = new FileStream(filename,
        FileMode.OpenOrCreate);
        DataContractSerializer ser =
            new DataContractSerializer(typeof(Person));
        ser.WriteObject(writer, p1);
        writer.Close();
    }

    public static void ReadObject(string filename)
    {
        // Deserialize an instance of the Person class
        // from an XML file.
        FileStream fs = new FileStream(filename,
        FileMode.OpenOrCreate);
        DataContractSerializer ser =
            new DataContractSerializer(typeof(Person));
        // Deserialize the data and read it from the instance.
        Person deserializedPerson = (Person)ser.ReadObject(fs);
        fs.Close();
        Console.WriteLine(String.Format("{0} {1}, ID: {2}",
        deserializedPerson.FirstName, deserializedPerson.LastName,
        deserializedPerson.IdNumber));
    }
}

Imports System.Collections
Imports System.IO
Imports System.Runtime.Serialization
Imports System.Xml

' You must apply a DataContractAttribute or SerializableAttribute
' to a class to have it serialized by the DataContractSerializer.
<DataContract()>  _
Class Person
    Implements IExtensibleDataObject

    Private LastNameValue As String
     
    ' Apply the DataMemberAttribute to fields (or properties) 
    ' that must be serialized.
    
    <DataMember()>  _
    Public FirstName As String
    
    <DataMember()>  _
    Public Property LastName() As String
        Get
            Return LastNameValue 
        End Get

        Set(ByVal Value As String)
           LastNameValue = Value
        End Set
    End Property

    
    <DataMember(Name:="ID")>  _
    Public IdNumber As Integer
    
    ' Note that you can apply the DataMemberAttribute to 
    ' a private field as well.
    <DataMember()>  _
    Private Secret As String
    
    Public Sub New(ByVal newfName As String, ByVal newLName As String, ByVal newIdNumber As Integer) 
        FirstName = newfName
        LastName = newLName
        IdNumber = newIdNumber
        Secret = newfName + newLName + newIdNumber.ToString()
    
    End Sub 
    
    ' The ExtensionData field holds data from future versions 
    ' of the type.  This enables this type to be compatible with 
    ' future versions. The field is required to implement the 
    ' IExtensibleObjectData interface.
    Private extensionDataValue As ExtensionDataObject
    
    Public Property ExtensionData() As ExtensionDataObject _
       Implements IExtensibleDataObject.ExtensionData
        Get
            Return extensionDataValue
        End Get
        Set
            extensionDataValue = value
        End Set
    End Property
End Class 

Public Class Test
    Public Shared Sub Main(ByVal args() As String) 
        Try
            ReadObject("DataMemberAttributeExample.xml")
            WriteObject("DataMemberAttributeExample.xml")
        Catch exc As Exception
            Console.WriteLine("The serialization operation failed: {0} StackTrace: {1}", _
            exc.Message, exc.StackTrace)
        Finally
            Console.WriteLine("Press <Enter> to exit....")
            Console.ReadLine()
        End Try
    End Sub 
    
    Public Shared Sub ReadObject(ByVal filename As String) 
        ' Create a new instance of the Person class.
        Dim p1 As New Person("Zighetti", "Barbara", 101)
        Dim writer As New FileStream(filename, FileMode.Create)
        Dim ser As New DataContractSerializer(GetType(Person))
        ser.WriteObject(writer, p1)
        writer.Close()
    End Sub 

    Public Shared Sub WriteObject(ByVal filename As String) 
        ' Deserialize an instance of the Person class 
        ' from an XML file.
        Dim fs As New FileStream(filename, FileMode.OpenOrCreate)
        Dim ser As New DataContractSerializer(getTYpe(Person))
        ' Deserialize the data and read it from the instance.
        Dim deserializedPerson As Person = ser.ReadObject(fs)
        fs.Close()
        Console.WriteLine(String.Format("{0} {1}, ID: {2}", _
        deserializedPerson.FirstName, deserializedPerson.LastName, deserializedPerson.IdNumber))
    End Sub 
End Class

Remarks

Apply the DataMemberAttribute attribute in conjunction with the DataContractAttribute to identify members of a type that are part of a data contract. One of the serializers that can serialize data contracts is the DataContractSerializer.

The data contract model is an "opt-in" model. Applying the DataMemberAttribute to a field or property explicitly specifies that the member value will be serialized. In contrast, the XmlSerializer serializes all public fields and properties of a type.

Caution

You can apply the DataMemberAttribute to private fields or properties. Be aware that the data returned by the member (even if it's private) will be serialized and deserialized, and thus can be viewed or intercepted by a malicious user or process.

By default, the CLR member name is used as the name of the data member. By setting the Name property, you can customize the name of the data member. This can be used to provide a name that may not be allowed as a CLR member name. When mapping to XML using the DataContractSerializer, this name is used as the name of the schema element in a type.

Note

Properties to which the DataMemberAttribute attribute has been applied must have both get and set fields. They cannot be get-only or set-only. To serialize a property that should remain get-only by design (for example, a property that returns a collection), consider applying the DataMemberAttribute to the backing field instead.

For more information about data contracts and data members, see Using Data Contracts. For more information about member names, see Data Member Default Values.

Constructors

DataMemberAttribute()

Initializes a new instance of the DataMemberAttribute class.

Properties

EmitDefaultValue	Gets or sets a value that specifies whether to serialize the default value for a field or property being serialized.
IsNameSetExplicitly	Gets whether Name has been explicitly set.
IsRequired	Gets or sets a value that instructs the serialization engine that the member must be present when reading or deserializing.
Name	Gets or sets a data member name.
Order	Gets or sets the order of serialization and deserialization of a member.
TypeId	When implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute)

Methods

Equals(Object)	Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute)
GetHashCode()	Returns the hash code for this instance. (Inherited from Attribute)
GetType()	Gets the Type of the current instance. (Inherited from Object)
IsDefaultAttribute()	When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute)
Match(Object)	When overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
ToString()	Returns a string that represents the current object. (Inherited from Object)

See also

• DataContractAttribute
• DataContractSerializer
• IExtensibleDataObject
• Using Data Contracts
• Best Practices: Data Contract Versioning
• Data Member Default Values
• Data Member Order