Help Opening PDF file on browser

Question

 

Hi, I have a class that implements a thread which check whether a certain file exist or not (pdf file). If the file exist the thread should open the file on the browser then kill itself (the thread) but Im having a problem with Response.WriteFile() method, I always encountering an error saying "object not set to an instance." I'll Attach my code here.Please Help ASAP. Thanks

FIRST CLASS

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FileTracker f = new FileTracker("c:\\Temp\\BCS_Temp.pdf");
f.createFinder();
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SECOND CLASS

using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;

//--
using System.Threading;
using System.IO;

namespace ThreadTest
{

 /// <summary>
 /// Summary description for Finder.
 /// </summary>
 ///
 public class FileTracker
 {
  public static string m_strRptFile;
  static Thread thread;
  public FileTracker(string FileName)
  {
   //
   // TODO: Add constructor logic here
   //
   m_strRptFile = FileName;
   
  }

  public void ThreadStart()
  {
   FindFileExist();
  }

  public void createFinder()
  {
   FileTracker f = new FileTracker(m_strRptFile);
   thread   = new Thread(new ThreadStart(f.ThreadStart));
   thread.Priority = System.Threading.ThreadPriority.Lowest;
   thread.Start();
  }

public void FindFileExist()
  {
   
   for(;;)
   {
    if(File.Exists(m_strRptFile))
    {
     //WebForm1.strF =  m_strRptFile;
     
     HttpContext.Current.Response.ClearContent();
     HttpContext.Current.Response.ClearHeaders();
     HttpContext.Current.Response.ContentType = "application/pdf";
     HttpContext.Current.Response.WriteFile(strF);
     
     HttpContext.Current.Response.Flush();
     HttpContext.Current.Response.Close();
     thread.Abort();  
    }
   }

}

}
}