how to access the duration property?

Hi,
 
Please check the below code and solve my problem.

 
Class file

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.IO;
namespace Refresh.FlashTools
{
/// <summary>
/// Reads the meta information embedded in an FLV file
// ...