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SerializationBinder Class

Allows users to control class loading and mandate what class to load.

For a list of all members of this type, see SerializationBinder Members.

System.Object
   System.Runtime.Serialization.SerializationBinder

[Visual Basic]
<Serializable>
MustInherit Public Class SerializationBinder
[C#]
[Serializable]
public abstract class SerializationBinder
[C++]
[Serializable]
public __gc __abstract class SerializationBinder
[JScript]
public
   Serializable
abstract class SerializationBinder

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Remarks

During serialization, a formatter transmits the information required to create an instance of an object of the correct type and version. This information generally includes the full type name and assembly name of the object. The assembly name includes the name, version, and strong name (see Strong-Named Assemblies) hash of the assembly. By default, deserialization uses this information to create an instance of an identical object (with the exception of any assembly loading restricted by the security policy). Some users need to control which class to load, either because the class has moved between assemblies or a different version of the class is required on the server and client.

This is an abstract base class. All binders extend this class.

Notes to Inheritors:  When you inherit from SerializationBinder, you must override the following member: BindToType.

Example

[Visual Basic] 
Imports System
Imports System.IO
Imports System.Runtime.Serialization
Imports System.Runtime.Serialization.Formatters.Binary
Imports System.Reflection
Imports System.Security.Permissions

Class App
   <STAThread()> Shared Sub Main()
      Serialize()
      Deserialize()
   End Sub


   Shared Sub Serialize()
      ' To serialize the objects, you must first open a stream for writing. 
      ' Use a file stream here.
      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

         ' Construct a Version1Type object and serialize it.
         Dim obj As New Version1Type
         obj.x = 123
         formatter.Serialize(fs, obj)
      Catch e As SerializationException
         Console.WriteLine("Failed to serialize. Reason: " & e.Message)
         Throw
      Finally
         fs.Close()
      End Try
   End Sub


   Shared Sub Deserialize()
      ' Declare the Version2Type reference.
      Dim obj As Version2Type = Nothing

      ' Open the file containing the data that you want to deserialize.
      Dim fs As New FileStream("DataFile.dat", FileMode.Open)
      Try
         ' Construct a BinaryFormatter and use it 
         ' to deserialize the data from the stream.
         Dim formatter As New BinaryFormatter

         ' Construct an instance of the 
         ' Version1ToVersion2TypeSerialiationBinder type.
         ' This Binder type can deserialize a Version1Type  
         ' object to a Version2Type object.
         formatter.Binder = New Version1ToVersion2DeserializationBinder

         obj = DirectCast(formatter.Deserialize(fs), Version2Type)
      Catch e As SerializationException
         Console.WriteLine("Failed to deserialize. Reason: " & e.Message)
         Throw
      Finally
         fs.Close()
      End Try

      ' To prove that a Version2Type object was deserialized, 
      ' display the object's type and fields to the console.
      Console.WriteLine("Type of object deserialized: {0}", obj.GetType())
      Console.WriteLine("x = {0}, name = {1}", obj.x, obj.name)
   End Sub
End Class


<Serializable()> Class Version1Type
   Public x As Int32
End Class


<Serializable()> Class Version2Type
   Implements ISerializable
   Public x As Int32
   Public name As String

   ' The security attribute demands that code that calls  
   ' this method have permission to perform serialization.
   <SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter:=True)> _
   Private Sub GetObjectData(ByVal info As SerializationInfo, _
         ByVal context As StreamingContext) Implements ISerializable.GetObjectData
      info.AddValue("x", x)
      info.AddValue("name", name)
   End Sub

   ' The security attribute demands that code that calls  
   ' this method have permission to perform serialization.
   <SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter:=True)> _
   Private Sub New(ByVal info As SerializationInfo, _
         ByVal context As StreamingContext)
      x = info.GetInt32("x")
      Try
         name = info.GetString("name")
      Catch e As SerializationException
         ' The "name" field was not serialized because 
         ' Version1Type did not contain this field.
         ' Set this field to a reasonable default value.
         name = "Reasonable default value"
      End Try
   End Sub
End Class


NotInheritable Class Version1ToVersion2DeserializationBinder
   Inherits SerializationBinder
   Public Overrides Function BindToType(ByVal assemblyName As String, _
         ByVal typeName As String) As Type

      Dim typeToDeserialize As Type = Nothing

      ' For each assemblyName/typeName that you want to deserialize
      ' to a different type, set typeToDeserialize to the desired type.
      Dim assemVer1 As String = [Assembly].GetExecutingAssembly().FullName
      Dim typeVer1 As String = GetType(Version1Type).FullName

      If assemblyName = assemVer1 And typeName = typeVer1 Then
         ' To use a type from a different assembly version, 
         ' change the version number.
         ' To do this, uncomment the following code.
         ' assemblyName = assemblyName.Replace("1.0.0.0", "2.0.0.0")

         ' To use a different type from the same assembly, 
         ' change the type name.
         typeName = typeName.Replace("Version1Type", "Version2Type")
      End If

      ' The following code returns the type.
      typeToDeserialize = Type.GetType(String.Format("{0}, {1}", typeName, _
                                       assemblyName))

      Return typeToDeserialize
   End Function
End Class

[C#] 
using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Reflection;
using System.Security.Permissions;


class App 
{
    [STAThread]
    static void Main() 
    {
        Serialize();
        Deserialize();
    }

    static void Serialize() 
    {
        // To serialize the objects, you must first open a stream for writing. 
        // Use a file stream here.
        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();

            // Construct a Version1Type object and serialize it.
            Version1Type obj = new Version1Type();
            obj.x = 123;
            formatter.Serialize(fs, obj);
        }
        catch (SerializationException e) 
        {
            Console.WriteLine("Failed to serialize. Reason: " + e.Message);
            throw;
        }
        finally 
        {
            fs.Close();
        }
    }

   
    static void Deserialize() 
    {
        // Declare the Version2Type reference.
        Version2Type obj = null;

        // Open the file containing the data that you want to deserialize.
        FileStream fs = new FileStream("DataFile.dat", FileMode.Open);
        try 
        {
            // Construct a BinaryFormatter and use it 
            // to deserialize the data from the stream.
            BinaryFormatter formatter = new BinaryFormatter();

            // Construct an instance of our the
            // Version1ToVersion2TypeSerialiationBinder type.
            // This Binder type can deserialize a Version1Type  
            // object to a Version2Type object.
            formatter.Binder = new Version1ToVersion2DeserializationBinder();

            obj = (Version2Type) formatter.Deserialize(fs);
        }
        catch (SerializationException e) 
        {
            Console.WriteLine("Failed to deserialize. Reason: " + e.Message);
            throw;
        }
        finally 
        {
            fs.Close();
        }

        // To prove that a Version2Type object was deserialized, 
        // display the object's type and fields to the console.
        Console.WriteLine("Type of object deserialized: " + obj.GetType());
        Console.WriteLine("x = {0}, name = {1}", obj.x, obj.name);
    }
}


[Serializable]
class Version1Type 
{
    public Int32 x;
}


[Serializable]
class Version2Type : ISerializable 
{
    public Int32 x;
    public String name;
   
    // The security attribute demands that code that calls
    // this method have permission to perform serialization.
    [SecurityPermissionAttribute(SecurityAction.Demand,SerializationFormatter=true)]
    void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context) 
    {
        info.AddValue("x", x);
        info.AddValue("name", name);
    }

    // The security attribute demands that code that calls  
    // this method have permission to perform serialization.
    [SecurityPermissionAttribute(SecurityAction.Demand,SerializationFormatter=true)]
    private Version2Type(SerializationInfo info, StreamingContext context) 
    {
        x = info.GetInt32("x");
        try 
        {
            name = info.GetString("name");
        }
        catch (SerializationException) 
        {
            // The "name" field was not serialized because Version1Type 
            // did not contain this field.
            // Set this field to a reasonable default value.
            name = "Reasonable default value";
        }
    }
}


sealed class Version1ToVersion2DeserializationBinder : SerializationBinder 
{
    public override Type BindToType(string assemblyName, string typeName) 
    {
        Type typeToDeserialize = null;

        // For each assemblyName/typeName that you want to deserialize to
        // a different type, set typeToDeserialize to the desired type.
        String assemVer1 = Assembly.GetExecutingAssembly().FullName;
        String typeVer1 = "Version1Type";

        if (assemblyName == assemVer1 && typeName == typeVer1) 
        {
            // To use a type from a different assembly version, 
            // change the version number.
            // To do this, uncomment the following line of code.
            // assemblyName = assemblyName.Replace("1.0.0.0", "2.0.0.0");

            // To use a different type from the same assembly, 
            // change the type name.
            typeName = "Version2Type";
        }

        // The following line of code returns the type.
        typeToDeserialize = Type.GetType(String.Format("{0}, {1}", 
            typeName, assemblyName));

        return typeToDeserialize;
    }
}

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

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

__sealed __gc class Version1ToVersion2DeserializationBinder;

[Serializable]
__gc class Version1Type
{
public:
    Int32 x;
};

[Serializable]
__gc class Version2Type : public ISerializable
{
public:
    Int32 x;
    String* name;

    // The security attribute demands that code that calls  
    // this method have permission to perform serialization.
    [SecurityPermissionAttribute(SecurityAction::Demand, SerializationFormatter=true)]
    void GetObjectData(SerializationInfo* info, StreamingContext context) 
    {
        info->AddValue(S"x", x);
        info->AddValue(S"name", name);
    }

    // The security attribute demands that code that calls  
    // this method have permission to perform serialization.
private:
    [SecurityPermissionAttribute(SecurityAction::Demand, SerializationFormatter=true)]
    Version2Type(SerializationInfo* info, StreamingContext context) 
    {
        x = info->GetInt32(S"x");
        try 
        {
            name = info->GetString(S"name");
        } 
        catch (SerializationException*) 
        {
            // The 'name' field was not serialized because Version1Type 
            // did not contain this field.
            // We will set this field to a reasonable default value.
            name = "Reasonable default value";
        }
    }
};

__sealed __gc class Version1ToVersion2DeserializationBinder : public SerializationBinder 
{
public:
    Type* BindToType(String* assemblyName, String* typeName) 
    {
        Type* typeToDeserialize = 0;

        // For each assemblyName/typeName that you want to deserialize to
        // a different type, set typeToDeserialize to the desired type.
        String* assemVer1 = Assembly::GetExecutingAssembly()->FullName;
        String* typeVer1 = "Version1Type";

        if (assemblyName->Equals(assemVer1) && typeName->Equals(typeVer1))
        {
            // To use a type from a different assembly version, 
            // change the version number using the following line of code.
            // assemblyName = assemblyName.Replace("1.0.0.0", "2.0.0.0");

            // To use a different type from the same assembly, 
            // change the type name.
            typeName = "Version2Type";
        }

        // The following line of code returns the type.
        typeToDeserialize = Type::GetType(String::Format("{0}, {1}", 
            typeName, assemblyName));

        return typeToDeserialize;
    }
};

__gc class App 
{
public:
    static void Serialize() 
    {
        // To serialize the objects, you must first open a stream for writing. 
        // We will use a file stream here.
        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();

            // Construct a Version1Type Object and serialize it.
            Version1Type* obj = new Version1Type();
            obj->x = 123;
            formatter->Serialize(fs, obj);
        } 
        catch (SerializationException* e) 
        {
            Console::WriteLine(S"Failed to serialize. Reason: {0}", e->Message);
            throw;
        }
        __finally 
        {
            fs->Close();
        }
    }

    static void Deserialize() 
    {
        // Declare the Version2Type reference.
        Version2Type* obj = 0;

        // Open the file containing the data that we want to deserialize.
        FileStream* fs = new FileStream(S"DataFile.dat", FileMode::Open);
        try 
        {
            // Construct a BinaryFormatter and use it 
            // to deserialize the data from the stream.
            BinaryFormatter* formatter = new BinaryFormatter();

            // Construct an instance of our 
            // Version1ToVersion2TypeSerialiationBinder type.
            // This Binder type knows how to deserialize a Version1Type  
            // Object* to a Version2Type Object.
            formatter->Binder = new Version1ToVersion2DeserializationBinder();

            obj = dynamic_cast<Version2Type*>(formatter->Deserialize(fs));
        }
        catch (SerializationException* e) 
        {
            Console::WriteLine(S"Failed to deserialize. Reason: {0}", e->Message);
            throw;
        }
        __finally 
        {
            fs->Close();
        }

        // To prove that a Version2Type Object* was deserialized, 
        // display the Object's type and fields to the console.
        Console::WriteLine(S"Type of Object deserialized: {0}", obj->GetType());
        Console::WriteLine(S"x = {0}, name = {1}", __box(obj->x), obj->name);
    }
};

[STAThread]
int main() 
{
    App::Serialize();
    App::Deserialize();
    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

Namespace: System.Runtime.Serialization

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

Assembly: Mscorlib (in Mscorlib.dll)

See Also

SerializationBinder Members | System.Runtime.Serialization Namespace | StrongName

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