Itextsharp File Attachment Event

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using iTextSharp.text.pdf;
using iTextSharp.text;
using iTextSharp.text.xml;
using iTextSharp.text.pdf.events;
using System.IO;

public class FileAttachmentEvent : PdfPCellEventForwarder
{
    protected PdfWriter writer;
    protected PdfFileSpecification fs;
    protected String description;
    public FileAttachmentEvent(PdfWriter Writer, PdfFileSpecification Fs, String Description)
    {
        this.writer = Writer;
        this.fs = Fs;
        this.description = Description;
    }
    public void cellLayout(PdfPCell cell, Rectangle position, PdfContentByte[] canvases)
    {
        try
        {
            PdfAnnotation annonation = PdfAnnotation.CreateFileAttachment(writer, new Rectangle(position.GetLeft(20f), position.GetTop(15f),                    position.GetLeft(5f), position.GetTop(5f)), description, fs);
            annonation.Name = description;
            writer.AddAnnotation(annonation);
        }
        catch (IOException)
        {
            throw;
        }
    }
}