public interface IConvertorPlugin
{
      String Name { get; }
      String FileExtension { get; }
 
    Byte[] Convert(Byte[] anInput);        
}

namespace SampleConvertorPlugin
{
    public class SampleConvertorPlugin2 : IConvertorPlugin
    {
        string IConvertorPlugin.Name
        {
            get { return "FB2->Text"; }
        }
 
        string IConvertorPlugin.FileExtension
        {
            get { return ".txt"; }
        }
 
        /// <summary>
        /// Coverts .fb2 document into .txt document.
        /// </summary>
        /// <param name="fb2Data">Content of .fb2 document as byte array.</param>
        /// <returns>Content of .txt document as byte array.</returns>
        Byte[] IConvertorPlugin.Convert(Byte[] fb2Data)
        {
            String lContent = Encoding.UTF8.GetString(fb2Data);
 
            String lResult;
            XmlDocument lDocument = new XmlDocument();
            lDocument.LoadXml(lContent);
 
            // Do some transformation here
            StringBuilder sb = new StringBuilder();
 
            // Add content
            String s = lDocument.SelectSingleNode("FictionBook/description/title-info/book-title").InnerText;
            sb.AppendLine(s);
            sb.AppendLine();
 
            XmlNodeList lSections = lDocument.SelectNodes("FictionBook/body/section");
            if (lSections == null) return null;
            foreach (XmlNode lItem in lSections)
                WriteSection(lItem, sb);
 
            lResult = sb.ToString();
 
            return Encoding.UTF8.GetBytes(lResult);
        }
 
        private void WriteSection(XmlNode aNode, StringBuilder aStringBuilder)
        {
            foreach (XmlNode lNode in aNode.ChildNodes)
            {
                switch (lNode.Name)
                {
                    case "title":
                        aStringBuilder.AppendLine(lNode.InnerText);
                        break;
                    case "section":
                        fLevel++;
                        WriteSection(lNode, aStringBuilder);
                        break;
                    case "epigraph":
                        aStringBuilder.AppendLine(lNode.InnerText);
                        break;
                    case "subtitle":
                        aStringBuilder.AppendLine(lNode.InnerText);
                        break;
                    case "p":
                        aStringBuilder.AppendLine(lNode.InnerText);
                        break;
                }
            }
        }
    }
}