OnDeserializingAttribute Class
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OnDeserializingAttribute Class

 

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

Namespace:   System.Runtime.Serialization
Assembly:  mscorlib (in mscorlib.dll)

System.Object
  System.Attribute
    System.Runtime.Serialization.OnDeserializingAttribute

<AttributeUsageAttribute(AttributeTargets.Method, Inherited := False)>
<ComVisibleAttribute(True)>
Public NotInheritable Class OnDeserializingAttribute
	Inherits Attribute

NameDescription
System_CAPS_pubmethodOnDeserializingAttribute()

Initializes a new instance of the OnDeserializingAttribute class.

NameDescription
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_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_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.)

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:

<OnDeserializing()> _
Private Sub SetValuesOnDeserializing(ByVal context As StreamingContext)
    ' Code not shown.
End Sub
System_CAPS_noteNote

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()
            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.'

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 3.0
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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