OnDeserializedAttribute Class

Definition

Namespace:

System.Runtime.Serialization

Assembly:

System.Runtime.dll

When applied to a method, specifies that the method is called immediately after deserialization of an object in an object graph. The order of deserialization relative to other objects in the graph is non-deterministic.

public ref class OnDeserializedAttribute sealed : Attribute

[System.AttributeUsage(System.AttributeTargets.Method, Inherited=false)]
public sealed class OnDeserializedAttribute : Attribute

[<System.AttributeUsage(System.AttributeTargets.Method, Inherited=false)>]
type OnDeserializedAttribute = class
    inherit Attribute

Public NotInheritable Class OnDeserializedAttribute
Inherits Attribute

Inheritance

Object

Attribute

OnDeserializedAttribute

Attributes

AttributeUsageAttribute

Examples

The following example applies the OnDeserializedAttribute, OnSerializingAttribute, OnSerializedAttribute, and OnDeserializingAttribute attributes to methods in a class.

using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;

public class Test
{
    public static void Main()
    {
        // Create a new TestSimpleObject object.
        TestSimpleObject obj = new TestSimpleObject();

        Console.WriteLine("\n Before serialization the object contains: ");
        obj.Print();

        // Open a file and serialize the object into binary format.
        Stream stream = File.Open("DataFile.dat", FileMode.Create);
        BinaryFormatter formatter = new BinaryFormatter();

        try
        {
            formatter.Serialize(stream, obj);

            // Print the object again to see the effect of the 
            //OnSerializedAttribute.
            Console.WriteLine("\n After serialization the object contains: ");
            obj.Print();

            // Set the original variable to null.
            obj = null;
            stream.Close();

            // Open the file "DataFile.dat" and deserialize the object from it.
            stream = File.Open("DataFile.dat", FileMode.Open);

            // Deserialize the object from the data file.
            obj = (TestSimpleObject)formatter.Deserialize(stream);

            Console.WriteLine("\n After deserialization the object contains: ");
            obj.Print();
            Console.ReadLine();
        }
        catch (SerializationException se)
        {
            Console.WriteLine("Failed to serialize. Reason: " + se.Message);
            throw;
        }
        catch (Exception exc)
        {
            Console.WriteLine("An exception occurred. Reason: " + exc.Message);
            throw;
        }
        finally
        {
            stream.Close();
            obj = null;
            formatter = null;
        }
    }
}

// This is the object that will be serialized and deserialized.
[Serializable()]
public class TestSimpleObject
{
    // This member is serialized and deserialized with no change.
    public int member1;

    // The value of this field is set and reset during and 
    // after serialization.
    private string member2;

    // This field is not serialized. The OnDeserializedAttribute 
    // is used to set the member value after serialization.
    [NonSerialized()]
    public string member3;

    // This field is set to null, but populated after deserialization.
    private string member4;

    // Constructor for the class.
    public TestSimpleObject()
    {
        member1 = 11;
        member2 = "Hello World!";
        member3 = "This is a nonserialized value";
        member4 = null;
    }

    public void Print()
    {
        Console.WriteLine("member1 = '{0}'", member1);
        Console.WriteLine("member2 = '{0}'", member2);
        Console.WriteLine("member3 = '{0}'", member3);
        Console.WriteLine("member4 = '{0}'", member4);
    }

    [OnSerializing()]
    internal void OnSerializingMethod(StreamingContext context)
    {
        member2 = "This value went into the data file during serialization.";
    }

    [OnSerialized()]
    internal void OnSerializedMethod(StreamingContext context)
    {
        member2 = "This value was reset after serialization.";
    }

    [OnDeserializing()]
    internal void OnDeserializingMethod(StreamingContext context)
    {
        member3 = "This value was set during deserialization";
    }

    [OnDeserialized()]
    internal void OnDeserializedMethod(StreamingContext context)
    {
        member4 = "This value was set after deserialization.";
    }
}

// Output:
//  Before serialization the object contains: 
// member1 = '11'
// member2 = 'Hello World!'
// member3 = 'This is a nonserialized value'
// member4 = ''
//
//  After serialization the object contains: 
// member1 = '11'
// member2 = 'This value was reset after serialization.'
// member3 = 'This is a nonserialized value'
// member4 = ''
//
//  After deserialization the object contains: 
// member1 = '11'
// member2 = 'This value went into the data file during serialization.'
// member3 = 'This value was set during deserialization'
// member4 = 'This value was set after deserialization.'

Imports System.IO
Imports System.Runtime.Serialization
Imports System.Runtime.Serialization.Formatters.Binary

Public Class Test
    Public Shared Sub Main()
        ' Create a new TestSimpleObject object.
        Dim obj As New TestSimpleObject()

        Console.WriteLine(vbLf + " Before serialization the object contains: ")
        obj.Print()

        ' Open a file and serialize the object into binary format.
        Dim stream As Stream = File.Open("DataFile.dat", FileMode.Create)
        Dim formatter As New BinaryFormatter()

        Try
            formatter.Serialize(stream, obj)

            ' Print the object again to see the effect of the 
            'OnSerializedAttribute.
            Console.WriteLine(vbLf + " After serialization the object contains: ")
            obj.Print()

            ' Set the original variable to null.
            obj = Nothing
            stream.Close()

            ' Open the file "DataFile.dat" and deserialize the object from it.
            stream = File.Open("DataFile.dat", FileMode.Open)

            ' Deserialize the object from the data file.
            obj = CType(formatter.Deserialize(stream), TestSimpleObject)

            Console.WriteLine(vbLf + " After deserialization the object contains: ")
            obj.Print()
            Console.ReadLine()
        Catch se As SerializationException
            Console.WriteLine("Failed to serialize. Reason: " + se.Message)
            Throw
        Catch exc As Exception
            Console.WriteLine("An exception occurred. Reason: " + exc.Message)
            Throw
        Finally
            stream.Close()
            obj = Nothing
            formatter = Nothing
        End Try
    End Sub
End Class


' This is the object that will be serialized and deserialized.
<Serializable()> _
Public Class TestSimpleObject
    ' This member is serialized and deserialized with no change.
    Public member1 As Integer

    ' The value of this field is set and reset during and 
    ' after serialization.
    Private member2 As String

    ' This field is not serialized. The OnDeserializedAttribute 
    ' is used to set the member value after serialization.
    <NonSerialized()> _
    Public member3 As String

    ' This field is set to null, but populated after deserialization.
    Private member4 As String

    ' Constructor for the class.
    Public Sub New()
        member1 = 11
        member2 = "Hello World!"
        member3 = "This is a nonserialized value"
        member4 = Nothing
    End Sub

    Public Sub Print()
        Console.WriteLine("member1 = '{0}'", member1)
        Console.WriteLine("member2 = '{0}'", member2)
        Console.WriteLine("member3 = '{0}'", member3)
        Console.WriteLine("member4 = '{0}'", member4)
    End Sub

    <OnSerializing()> _
    Friend Sub OnSerializingMethod(ByVal context As StreamingContext)
        member2 = "This value went into the data file during serialization."
    End Sub

    <OnSerialized()> _
    Friend Sub OnSerializedMethod(ByVal context As StreamingContext)
        member2 = "This value was reset after serialization."
    End Sub

    <OnDeserializing()> _
    Friend Sub OnDeserializingMethod(ByVal context As StreamingContext)
        member3 = "This value was set during deserialization"
    End Sub

    <OnDeserialized()> _
    Friend Sub OnDeserializedMethod(ByVal context As StreamingContext)
        member4 = "This value was set after deserialization."
    End Sub
End Class

' Output:
'  Before serialization the object contains: 
' member1 = '11'
' member2 = 'Hello World!'
' member3 = 'This is a nonserialized value'
' member4 = ''
'
'  After serialization the object contains: 
' member1 = '11'
' member2 = 'This value was reset after serialization.'
' member3 = 'This is a nonserialized value'
' member4 = ''
'
'  After deserialization the object contains: 
' member1 = '11'
' member2 = 'This value went into the data file during serialization.'
' member3 = 'This value was set during deserialization'
' member4 = 'This value was set after deserialization.'

Remarks

Use the OnDeserializedAttribute when you need to fix values on a deserialized object after it has been deserialized and before the graph is returned. This attribute can be used instead of the IDeserializationCallback interface.

To use the OnDeserializedAttribute, the method must contain a StreamingContext parameter. The attribute marks the method to be called by the serialization infrastructure and the StreamingContext provides additional data about the type of serialization taking place. The usage is shown in the following code:

[OnDeserialized]
private void SetValuesOnDeserialized(StreamingContext context)
{
    // Code not shown.
}

<OnDeserialized()> _
Private Sub SetValuesOnDeserialized(ByVal context As StreamingContext)
    ' Code not shown.
End Sub

Note

In your code, you can use the word OnDeserialized instead of the longer OnDeserializedAttribute.

Constructors

OnDeserializedAttribute()

Initializes a new instance of the OnDeserializedAttribute class.

Properties

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

• BinaryFormatter
• OnDeserializingAttribute
• OnSerializedAttribute
• OnSerializingAttribute
• SoapFormatter