He pasado las últimas horas juntando el siguiente código después de leer mucho que parece desactualizado o que no parece funcionar.

Si hay alguna ayuda para alguien aquí es el código de trabajo final. Gratis para comentar si se puede mejorar: -)

public class SerializationHelper<T> {

#region static string SerializeObject( T obj, Encoding encoding )

/// <summary>
///   Serialize an [object] to an Xml String.
/// </summary>
/// <typeparam name="T">Object Type to Serialize</typeparam>
/// <param name="obj">Object Type to Serialize</param>
/// <param name="encoding">System.Text.Encoding Type</param>
/// <returns>Empty.String if Exception, XML string if successful</returns>
/// <example>
///   // UTF-16 Serialize
///   string xml = SerializationHelper<ObjectType>SerializeObject( [object], new UnicodeEncoding( false, false ) );
/// </example>
/// <example>
///   // UTF-8 Serialize
///   string xml = SerializationHelper<ObjectType>SerializeObject( [object], Encoding.UTF8 );
/// </example> 
public static string SerializeObject( T obj, Encoding encoding ) {

  if ( obj == null ) { return string.Empty; }

  try {

    XmlSerializer xmlSerializer = new XmlSerializer( typeof( T ) );

    using ( MemoryStream memoryStream = new MemoryStream() ) {

      XmlWriterSettings xmlWriterSettings = new XmlWriterSettings() { Encoding = encoding };

      using ( XmlWriter writer = XmlWriter.Create( memoryStream, xmlWriterSettings ) ) {

        xmlSerializer.Serialize( writer, obj );

      }

      return encoding.GetString( memoryStream.ToArray() );

    }

  }
  catch {

    return string.Empty;

  }

}

#endregion   

#region static T DeserializeObject( string xml, Encoding encoding )

/// <summary>
///   Deserialize an Xml String to an [object]
/// </summary>
/// <typeparam name="T">Object Type to Deserialize</typeparam>
/// <param name="xml">Xml String to Deserialize</param>
/// <param name="encoding">System.Text.Encoding Type</param>
/// <returns>Default if Exception, Deserialize object if successful</returns>
/// <example>
///   // UTF-16 Deserialize
///   [object] = SerializationHelper<ObjectType>DeserializeObject( xml, Encoding.Unicode )
/// </example>
/// <example>
///   // UTF-8 Deserialize
///   [object] = SerializationHelper<ObjectType>DeserializeObject( xml, Encoding.UTF8 )
/// </example> 
public static T DeserializeObject( string xml, Encoding encoding ) {

  if ( string.IsNullOrEmpty( xml ) ) { return default( T ); }

  try {

    XmlSerializer xmlSerializer = new XmlSerializer( typeof( T ) );

    using ( MemoryStream memoryStream = new MemoryStream( encoding.GetBytes( xml ) ) ) {

      // No settings need modifying here
      XmlReaderSettings  xmlReaderSettings  = new XmlReaderSettings();

      using ( XmlReader xmlReader = XmlReader.Create( memoryStream, xmlReaderSettings ) ) {

        return (T)xmlSerializer.Deserialize( xmlReader );

      }

    }

  }
  catch {

    return default( T );

  }

}

#endregion     

}