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ISerializable Interface

  • Reference

Definition

Namespace:
System.Runtime.Serialization
Assembly:
System.Runtime.dll
Assembly:
System.Runtime.Serialization.Formatters.dll
Assembly:
mscorlib.dll
Assembly:
netstandard.dll

Allows an object to control its own serialization and deserialization through binary and XML serialization.

public interface class ISerializable
public interface ISerializable
[System.Runtime.InteropServices.ComVisible(true)]
public interface ISerializable
type ISerializable = interface
[<System.Runtime.InteropServices.ComVisible(true)>]
type ISerializable = interface
Public Interface ISerializable
Derived
Attributes
ComVisibleAttribute

Examples

The following code example demonstrates the use of the ISerializable interface to define custom binary serialization behavior for a class.

using namespace System;
using namespace System::IO;
using namespace System::Collections;
using namespace System::Runtime::Serialization::Formatters::Binary;
using namespace System::Runtime::Serialization;

ref class SingletonSerializationHelper;

// There should be only one instance of this type per AppDomain.

[Serializable]
public ref class Singleton sealed: public ISerializable
{
private:

   // This is the one instance of this type.
   static Singleton^ theOneObject = gcnew Singleton;

public:

   // Here are the instance fields.
   String^ someString;
   Int32 someNumber;

private:

   // Private constructor allowing this type to construct the singleton.
   Singleton()
   {
      
      // Do whatever is necessary to initialize the singleton.
      someString = "This is a String* field";
      someNumber = 123;
   }

public:

   // A method returning a reference to the singleton.
   static Singleton^ GetSingleton()
   {
      return theOneObject;
   }

   // A method called when serializing a Singleton.
   [System::Security::Permissions::SecurityPermissionAttribute
   (System::Security::Permissions::SecurityAction::LinkDemand, 
   Flags=System::Security::Permissions::SecurityPermissionFlag::SerializationFormatter)]
   virtual void GetObjectData( SerializationInfo^ info, StreamingContext context )
   {
      // Instead of serializing this Object*, we will  
      // serialize a SingletonSerializationHelp instead.
      info->SetType( SingletonSerializationHelper::typeid );

      // No other values need to be added.
   }

   // NOTE: ISerializable*'s special constructor is NOT necessary 
   // because it's never called
};

[Serializable]
private ref class SingletonSerializationHelper sealed: public IObjectReference
{
public:

   // This Object* has no fields (although it could).
   // GetRealObject is called after this Object* is deserialized
   virtual Object^ GetRealObject( StreamingContext context )
   {
      // When deserialiing this Object*, return a reference to 
      // the singleton Object* instead.
      return Singleton::GetSingleton();
   }
};

[STAThread]
int main()
{
   FileStream^ fs = gcnew FileStream( "DataFile.dat",FileMode::Create );
   try
   {
      // Construct a BinaryFormatter and use it 
      // to serialize the data to the stream.
      BinaryFormatter^ formatter = gcnew BinaryFormatter;

      // Create an array with multiple elements refering to 
      // the one Singleton Object*.
      array<Singleton^>^a1 = {Singleton::GetSingleton(),Singleton::GetSingleton()};

      // This displays S"True".
      Console::WriteLine( "Do both array elements refer to the same Object? {0}", (a1[ 0 ] == a1[ 1 ]) );

      // Serialize the array elements.
      formatter->Serialize( fs, a1 );

      // Deserialize the array elements.
      fs->Position = 0;
      array<Singleton^>^a2 = (array<Singleton^>^)formatter->Deserialize( fs );

      // This displays S"True".
      Console::WriteLine( "Do both array elements refer to the same Object? {0}", (a2[ 0 ] == a2[ 1 ]) );

      // This displays S"True".
      Console::WriteLine( "Do all  array elements refer to the same Object? {0}", (a1[ 0 ] == a2[ 0 ]) );
   }
   catch ( SerializationException^ e ) 
   {
      Console::WriteLine( "Failed to serialize. Reason: {0}", e->Message );
      throw;
   }
   finally
   {
      fs->Close();
   }

   return 0;
}

using System;
using System.Text;
using System.IO;
// Add references to Soap and Binary formatters.
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization.Formatters.Soap ;
using System.Runtime.Serialization;

[Serializable]
public class MyItemType : ISerializable
{
    public MyItemType()
    {
        // Empty constructor required to compile.
    }

    // The value to serialize.
    private string myProperty_value;

    public string MyProperty
    {
        get { return myProperty_value; }
        set { myProperty_value = value; }
    }

    // Implement this method to serialize data. The method is called
    // on serialization.
    public void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        // Use the AddValue method to specify serialized values.
        info.AddValue("props", myProperty_value, typeof(string));
    }

    // The special constructor is used to deserialize values.
    public MyItemType(SerializationInfo info, StreamingContext context)
    {
        // Reset the property value using the GetValue method.
        myProperty_value = (string) info.GetValue("props", typeof(string));
    }
}

// This is a console application.
public static class Test
{
    static void Main()
    {
        // This is the name of the file holding the data. You can use any file extension you like.
        string fileName = "dataStuff.myData";

        // Use a BinaryFormatter or SoapFormatter.
        IFormatter formatter = new BinaryFormatter();
        //IFormatter formatter = new SoapFormatter();

        Test.SerializeItem(fileName, formatter); // Serialize an instance of the class.
        Test.DeserializeItem(fileName, formatter); // Deserialize the instance.
        Console.WriteLine("Done");
        Console.ReadLine();
    }

    public static void SerializeItem(string fileName, IFormatter formatter)
    {
        // Create an instance of the type and serialize it.
        MyItemType t = new MyItemType();
        t.MyProperty = "Hello World";

        FileStream s = new FileStream(fileName , FileMode.Create);
        formatter.Serialize(s, t);
        s.Close();
    }

    public static void DeserializeItem(string fileName, IFormatter formatter)
    {
        FileStream s = new FileStream(fileName, FileMode.Open);
        MyItemType t = (MyItemType)formatter.Deserialize(s);
        Console.WriteLine(t.MyProperty);
    }
}

Imports System.Text
Imports System.IO

' Add references to Soap and Binary formatters.
Imports System.Runtime.Serialization.Formatters.Binary
Imports System.Runtime.Serialization.Formatters.Soap
Imports System.Runtime.Serialization


<Serializable()> _
Public Class MyItemType
    Implements ISerializable
    ' Empty constructor required to compile.
    Public Sub New()
    End Sub

    ' The value to serialize.
    Private myProperty_value As String

    Public Property MyProperty() As String
        Get
            Return myProperty_value
        End Get
        Set(value As String)
            myProperty_value = value
        End Set
    End Property

    ' Implement this method to serialize data. The method is called 
    ' on serialization.
    Public Sub GetObjectData(info As SerializationInfo, context As StreamingContext) Implements ISerializable.GetObjectData
        ' Use the AddValue method to specify serialized values.
        info.AddValue("props", myProperty_value, GetType(String))

    End Sub

    ' The special constructor is used to deserialize values.
    Public Sub New(info As SerializationInfo, context As StreamingContext)
        ' Reset the property value using the GetValue method.
        myProperty_value = DirectCast(info.GetValue("props", GetType(String)), String)
    End Sub
End Class

' This is a console application. 
Public Class Test


    Public Shared Sub Main()
        ' This is the name of the file holding the data. You can use any file extension you like.
        Dim fileName As String = "dataStuff.myData"

        ' Use a BinaryFormatter or SoapFormatter.
        Dim formatter As IFormatter = New BinaryFormatter()
        ' Dim formatter As IFormatter = New SoapFormatter()

        Test.SerializeItem(fileName, formatter)
        ' Serialize an instance of the class.
        Test.DeserializeItem(fileName, formatter)
        ' Deserialize the instance.
        Console.WriteLine("Done")
        Console.ReadLine()
    End Sub

    Public Shared Sub SerializeItem(fileName As String, formatter As IFormatter)
        ' Create an instance of the type and serialize it.
        Dim myType As New MyItemType()
        myType.MyProperty = "Hello World"

        Dim fs As New FileStream(fileName, FileMode.Create)
        formatter.Serialize(fs, myType)
        fs.Close()
    End Sub


    Public Shared Sub DeserializeItem(fileName As String, formatter As IFormatter)
        Dim fs As New FileStream(fileName, FileMode.Open)

        Dim myType As MyItemType = DirectCast(formatter.Deserialize(fs), MyItemType)
        Console.WriteLine(myType.MyProperty)
    End Sub
End Class

Remarks

Any class that might be serialized using binary or XML serialization must be marked with the SerializableAttribute. If a class needs to control its binary or XML serialization process, it can implement the ISerializable interface. The Formatter calls the GetObjectData at serialization time and populates the supplied SerializationInfo with all the data required to represent the object. The Formatter creates a SerializationInfo with the type of the object in the graph. Objects that need to send proxies for themselves can use the FullTypeName and AssemblyName methods on SerializationInfo to change the transmitted information.

In the case of class inheritance, it is possible to serialize a class that derives from a base class that implements ISerializable. In this case, the derived class should call the base class implementation of GetObjectData inside its implementation of GetObjectData. Otherwise, the data from the base class will not be serialized.

The ISerializable interface implies a constructor with the signature constructor (SerializationInfo information, StreamingContext context). At deserialization time, the current constructor is called only after the data in the SerializationInfo has been deserialized by the formatter. In general, this constructor should be protected if the class is not sealed.

The order in which objects are deserialized cannot be guaranteed. For example, if one type references a type that has not been deserialized yet, an exception will occur. If you are creating types that have such dependencies, you can work around the problem by implementing the IDeserializationCallback interface and the OnDeserialization method.

The serialization architecture handles object types that extend MarshalByRefObject the same as types that extend Object. These types can be marked with the SerializableAttribute and implement the ISerializable interface as any other object type. Their object state will be captured and persisted onto the stream.

When these types are being used through System.Runtime.Remoting, the remoting infrastructure provides a surrogate that preempts typical serialization and instead serializes a proxy to the MarshalByRefObject. A surrogate is a helper that knows how to serialize and deserialize objects of a particular type. The proxy, invisible to the user in most cases, will be of type ObjRef.

As a general design pattern, it would be unusual for a class to be both marked with the serializable attribute and extend MarshalByRefObject. Developers should think carefully about the possible serialization and remoting scenarios when combining these two characteristics. One example where this might be applicable is with a MemoryStream. While the base class of MemoryStream (Stream) extends from MarshalByRefObject, it is possible to capture the state of a MemoryStream and restore it at will. It might, therefore, be meaningful to serialize the state of this stream into a database and restore it at some later point in time. However, when used through remoting, an object of this type would be proxied.

For more information about serialization of classes that extend MarshalByRefObject, see RemotingSurrogateSelector. For more information about implementing ISerializable, see Custom Serialization.

Note

This interface does not apply to JSON serialization using System.Text.Json.

Notes to Implementers

Implement this interface to allow an object to take part in its own serialization and deserialization.

Methods

GetObjectData(SerializationInfo, StreamingContext)
Obsolete.

Populates a SerializationInfo with the data needed to serialize the target object.

Applies to

See also