While the example above shows one way to implement ISerializable, it is often better in C# to implement ISerializable.GetObjectData explicity and have that call a protected method or in Visual Basic implement ISerializable.GetObjectData directly using a protected method. This saves you from polluting your class's public API with methods that consumers will never need to call directly.

The following example shows a class that does this.

[C#]

using System;
using System.Security.Permissions;
using System.Runtime.Serialization;

namespace Samples
{
    [Serializable]
    public class Book : ISerializable
    {
        private string _Text;

        public Book(string text)
        {
            if (text == null)
                throw new ArgumentNullException("text");

            _Text = text;
        }

        protected Book(SerializationInfo info, StreamingContext context)
        {
            if (info == null)
                throw new ArgumentNullException("info");

            _Text = info.GetString("Text");            
        }

        public string Text
        {
            get { return _Text; }
        }

        protected virtual void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            info.AddValue("Text", _Text);
        }

        [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.SerializationFormatter)]
        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
        {
            if (info == null)
                throw new ArgumentNullException("info");

            GetObjectData(info, context);
        }
    }
}

[Visual Basic]

Imports System
Imports System.Security.Permissions
Imports System.Runtime.Serialization

Namespace Samples

    <Serializable()> _
    Public Class Book
        Implements ISerializable

        Private _Text As String

        Public Sub New(ByVal text As String)

            If (text Is Nothing) Then Throw New ArgumentNullException("text")

  
            _Text = text

        End Sub

        Protected Sub New(ByVal info As SerializationInfo, ByVal context As StreamingContext)

            If (info Is Nothing) Then Throw New ArgumentNullException("info")

            _Text = info.GetString("Text")

        End Sub

        Public ReadOnly Property Text() As String
            Get
                Return _Text
            End Get
        End Property

  
        <SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags:=SecurityPermissionFlag.SerializationFormatter)> _
        Protected Overridable Sub GetObjectData(ByVal info As SerializationInfo, ByVal context As StreamingContext) _ 

            Implements ISerializable.GetObjectData

            If (info Is Nothing) Then Throw New ArgumentNullException("info")

            info.AddValue("Text", _Text)

        End Sub

    End Class

End Namespace

The hardest part about developing serializable classes, is testing that ISerializable has actually been implemented correctly. To help you do this, make use of the following helper method that tests the serialization of an object by serializing to and then deserializing from a binary stream directly in memory. This will cause both the serialization constructor and ISerializable.GetObjectData implementation to be called.

  [C#]

  using System.IO;
  using System.Runtime.Serialization.Formatters.Binary;

  public static class SerializationTester
  {
      public static T RoundTrip<T>(T value)
      {
          if (value == null)
              throw new ArgumentNullException("value");

          using (MemoryStream stream = new MemoryStream())
          {
              BinaryFormatter formatter = new BinaryFormatter();
              formatter.Serialize(stream, value);

              stream.Seek(0, SeekOrigin.Begin);

              return (T)formatter.Deserialize(stream);
          }
      }
  }

  [Visual Basic]

  Imports System.IO
  Imports System.Runtime.Serialization.Formatters.Binary

  Public Module SerializationTester

      Public Function RoundTrip(Of T)(ByVal value As T) As T
          If value Is Nothing Then Throw New ArgumentNullException("value")

          Using stream As New MemoryStream()

  
              Dim formatter As New BinaryFormatter()

              formatter.Serialize(stream, value)

              stream.Seek(0, SeekOrigin.Begin)

              Return DirectCast(formatter.Deserialize(stream), T)

  
          End Using

  
      End Function

  
  End Module

This allows you to do the following (this block uses the Book class from above).

  [C#]

  Book book = new Book("This is the book's text.");

  book = SerializationTester.RoundTrip(book);

  Console.WriteLine(book.Text);

  [Visual Basic]

  Dim book As New Book("This is the book's text.")

  book = SerializationTester.RoundTrip(book)

  Console.WriteLine(book.Text)

The above example outputs the following:

  This is the book's text.