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SerializationInfo.SetType Method

Sets the Type of the object to serialize.

[Visual Basic]
Public Sub SetType( _
   ByVal type As Type _
)
[C#]
public void SetType(
 Type type
);
[C++]
public: void SetType(
 Type* type
);
[JScript]
public function SetType(
   type : Type
);

Parameters

type
The Type of the object to serialize.

Exceptions

Exception Type Condition
ArgumentNullException The type parameter is a null reference (Nothing in Visual Basic).

Remarks

The Formatter is responsible for setting the Type of the SerializationInfo before passing it to GetObjectData. However, users who want to send proxies for their objects will need to change the type represented by this SerializationInfo. Using the SetType method is equivalent to setting both the FullTypeName and the AssemblyName.

Example

[Visual Basic] 
Imports System
Imports System.IO
Imports System.Collections
Imports System.Runtime.Serialization.Formatters.Binary
Imports System.Runtime.Serialization


' There should be only one instance of this type per AppDomain.
<Serializable()> Public NotInheritable Class Singleton
   Implements ISerializable

   ' This is the one instance of this type.
   Private Shared ReadOnly theOneObject As New Singleton

   ' Here are the instance fields.
   Public someString As String
   Public someNumber As Int32

   ' Private constructor allowing this type to construct the Singleton.
   Private Sub New()
      ' Do whatever is necessary to initialize the Singleton.
      someString = "This is a string field"
      someNumber = 123
   End Sub

   ' A method returning a reference to the Singleton.
   Public Shared Function GetSingleton() As Singleton
      Return theOneObject
   End Function

   ' A method called when serializing a Singleton.
   Private Sub GetObjectData(ByVal info As SerializationInfo, _
      ByVal context As StreamingContext) _
      Implements ISerializable.GetObjectData

      ' Instead of serializing this object, we will  
      ' serialize a SingletonSerializationHelp instead.
      info.SetType(GetType(SingletonSerializationHelper))
      ' No other values need to be added.
   End Sub

   ' Note: ISerializable's special constructor is not necessary 
   ' because it is never called.
End Class


<Serializable()> Friend NotInheritable Class SingletonSerializationHelper
   Implements IObjectReference
   ' This object has no fields (although it could).

   ' GetRealObject is called after this object is deserialized.
   Public Function GetRealObject(ByVal context As StreamingContext) As Object Implements IObjectReference.GetRealObject
      ' When deserialiing this object, return a reference to 
      ' the Singleton object instead.
      Return Singleton.GetSingleton()
   End Function
End Class


Class App
   <STAThread()> Shared Sub Main()
      Dim fs As New FileStream("DataFile.dat", FileMode.Create)

      Try
         ' Construct a BinaryFormatter and use it 
         ' to serialize the data to the stream.
         Dim formatter As New BinaryFormatter

         ' Create an array with multiple elements refering to 
         ' the one Singleton object.
         Dim a1() As Singleton = {Singleton.GetSingleton(), Singleton.GetSingleton()}

         ' This displays "True".
         Console.WriteLine("Do both array elements refer to the same object? " & _
            Object.ReferenceEquals(a1(0), a1(1)))

         ' Serialize the array elements.
         formatter.Serialize(fs, a1)

         ' Deserialize the array elements.
         fs.Position = 0
         Dim a2() As Singleton = DirectCast(formatter.Deserialize(fs), Singleton())

         ' This displays "True".
         Console.WriteLine("Do both array elements refer to the same object? " & _
            Object.ReferenceEquals(a2(0), a2(1)))

         ' This displays "True".
         Console.WriteLine("Do all array elements refer to the same object? " & _
            Object.ReferenceEquals(a1(0), a2(0)))
      Catch e As SerializationException
         Console.WriteLine("Failed to serialize. Reason: " & e.Message)
         Throw
      Finally
         fs.Close()
      End Try
   End Sub
End Class

[C#] 
using System;
using System.IO;
using System.Collections;
using System.Runtime.Serialization.Formatters.Binary;
using System.Runtime.Serialization;


// 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.
    public String someString;
    public Int32 someNumber;

    // Private constructor allowing this type to construct the Singleton.
    private Singleton() 
    { 
        // Do whatever is necessary to initialize the Singleton.
        someString = "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 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();
        }
    }
}

[C++] 
#using <mscorlib.dll>

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


private __sealed __gc class SingletonSerializationHelper;

// There should be only one instance of this type per AppDomain.
[Serializable]
public __sealed __gc 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]
    private __sealed __gc 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;
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

SerializationInfo Class | SerializationInfo Members | System.Runtime.Serialization Namespace

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