Export (0) Print
Expand All

ISerializable Interface

Allows an object to control its own serialization and deserialization.

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

[ComVisibleAttribute(true)]
public interface ISerializable

Any class that might be serialized must be marked with the SerializableAttribute. If a class needs to control its 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 [<topic://cpconCustomSerialization>].

Notes to Implementers:

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

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

using System;
using System.Web;
using System.IO;
using System.Collections;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;
using System.Security.Permissions;


// There should be only one instance of this type per AppDomain.
[Serializable]
public sealed class Singleton : ISerializable 
{
    // This is the one instance of this type. 
    private static readonly Singleton theOneObject = new Singleton();

    // Here are the instance fields. 
    private string someString_value;
    private Int32 someNumber_value;

   public string SomeString
   {
       get{return someString_value;}
       set{someString_value = value;}
   }

   public Int32 SomeNumber
   {
       get{return someNumber_value;}
       set{someNumber_value = value;}
   }

    // Private constructor allowing this type to construct the Singleton. 
    private Singleton() 
    { 
        // Do whatever is necessary to initialize the Singleton.
        someString_value = "This is a string field";
        someNumber_value = 123;
    }

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

    // A method called when serializing a Singleton.
    [SecurityPermissionAttribute(SecurityAction.LinkDemand, 
    Flags=SecurityPermissionFlag.SerializationFormatter)]
    void ISerializable.GetObjectData(
        SerializationInfo info, StreamingContext context) 
    {
        // Instead of serializing this object,  
        // serialize a SingletonSerializationHelp instead.
        info.SetType(typeof(SingletonSerializationHelper));
        // No other values need to be added.
    }

    // Note: ISerializable's special constructor is not necessary  
    // because it is never called.
}


[Serializable]
internal sealed class SingletonSerializationHelper : IObjectReference 
{
    // This object has no fields (although it could). 

    // GetRealObject is called after this object is deserialized. 
    public Object GetRealObject(StreamingContext context) 
    {
        // When deserialiing this object, return a reference to  
        // the Singleton object instead. 
        return Singleton.GetSingleton();
    }
}


class App 
{
    [STAThread]
    static void Main() 
    {
        FileStream fs = new FileStream("DataFile.dat", FileMode.Create);

        try 
        {
            // Construct a BinaryFormatter and use it  
            // to serialize the data to the stream.
            BinaryFormatter formatter = new BinaryFormatter();

            // Create an array with multiple elements refering to  
            // the one Singleton object.
            Singleton[] a1 = { Singleton.GetSingleton(), Singleton.GetSingleton() };

            // This displays "True".
            Console.WriteLine(
                "Do both array elements refer to the same object? " + 
                (a1[0] == a1[1]));     

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

            // Deserialize the array elements.
            fs.Position = 0;
            Singleton[] a2 = (Singleton[]) formatter.Deserialize(fs);

            // This displays "True".
            Console.WriteLine("Do both array elements refer to the same object? " 
                + (a2[0] == a2[1])); 

            // This displays "True".
            Console.WriteLine("Do all array elements refer to the same object? " 
                + (a1[0] == a2[0]));
        }   
        catch (SerializationException e) 
        {
            Console.WriteLine("Failed to serialize. Reason: " + e.Message);
            throw;
        }
        finally 
        {
            fs.Close();
        }
    }
}
#using <mscorlib.dll>
#using <System.dll>
#using <System.Web.dll>

using namespace System;
using namespace System::Web;
using namespace System::IO;
using namespace System::Collections;
using namespace System::Runtime::Serialization::Formatters::Binary;
using namespace System::Runtime::Serialization;
using namespace System::Security::Permissions;


private __sealed __gc class SingletonSerializationHelper;

// There should be only one instance of this type per AppDomain.
[Serializable]
[AspNetHostingPermission(SecurityAction::LinkDemand, 
    Level=AspNetHostingPermissionLevel::Minimal)]
public __gc __sealed class Singleton : public ISerializable 
{
	// This is the one instance of this type.
private:
	static Singleton* theOneObject = new Singleton();

	// Here are the instance fields.
public:
	String* someString;
	Int32 someNumber;

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

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

	// A method called when serializing a Singleton.
	void GetObjectData(SerializationInfo* info, StreamingContext context) 
	{
		// Instead of serializing this Object*, we will  
		// serialize a SingletonSerializationHelp instead.
		info->SetType(__typeof(SingletonSerializationHelper));
		// No other values need to be added.
	}

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

[Serializable]
[AspNetHostingPermission(SecurityAction::LinkDemand, 
   Level=AspNetHostingPermissionLevel::Minimal)]
private __gc __sealed class SingletonSerializationHelper : public IObjectReference 
	{
		// This Object* has no fields (although it could).
		// GetRealObject is called after this Object* is deserialized
	public:
		Object* GetRealObject(StreamingContext context) 
		{
			// When deserialiing this Object*, return a reference to 
			// the singleton Object* instead.
			return Singleton::GetSingleton();
		}
	};

[STAThread]
int main() 
{
	FileStream* fs = new FileStream(S"DataFile.dat", FileMode::Create);

	try 
	{
		// Construct a BinaryFormatter and use it 
		// to serialize the data to the stream.
		BinaryFormatter* formatter = new BinaryFormatter();

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

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

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

		// Deserialize the array elements.
		fs->Position = 0;
		Singleton* a2[] = (Singleton* __gc[]) formatter->Deserialize(fs);

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

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

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, 1.1, 1.0

Community Additions

ADD
Show:
© 2014 Microsoft