When applied to a method, specifies that the method is called during deserialization of an object.
Namespace:
System.Runtime.Serialization
Assembly:
mscorlib (in mscorlib.dll)
Visual Basic (Declaration)
<ComVisibleAttribute(True)> _
<AttributeUsageAttribute(AttributeTargets.Method, Inherited := False)> _
Public NotInheritable Class OnDeserializingAttribute _
Inherits Attribute
Dim instance As OnDeserializingAttribute
[ComVisibleAttribute(true)]
[AttributeUsageAttribute(AttributeTargets.Method, Inherited = false)]
public sealed class OnDeserializingAttribute : Attribute
[ComVisibleAttribute(true)]
[AttributeUsageAttribute(AttributeTargets::Method, Inherited = false)]
public ref class OnDeserializingAttribute sealed : public Attribute
public final class OnDeserializingAttribute extends Attribute
Use the OnDeserializingAttribute to set default values during deserialization. For example, if the type that you are deserializing does not contain a constructor, create a method to set values of any fields in the instance and apply the attribute to the method.
To use the OnDeserializingAttribute, 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:
\\ C#
[OnDeserializingAttribute()]
internal void RunThisMethod(StreamingContext context)
{
// Code not shown.
}
' Visual Basic
<OnDeserializingAttribute()> _
Private Sub RunThisMethod(context As StreamingContext)
' Code not shown.
End Sub
Note: |
|---|
In your code, you can use the word OnDeserializing instead of the longer OnDeserializingAttribute. |
The following example applies the OnDeserializedAttribute, OnSerializingAttribute, OnSerializedAttribute, and OnDeserializingAttribute attributes to methods in a class.
Imports System
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()
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.'
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();
}
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.'
System..::.Object
System..::.Attribute
System.Runtime.Serialization..::.OnDeserializingAttribute
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
.NET Framework
Supported in: 3.5, 3.0, 2.0
Reference