stream is closed get still error why?

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ASP.NET

The process cannot access the file 'C:\inetpub\wwwroot\wss\VirtualDirectories\80\Upload\mydoc_2013-05-03.doc' because it is being used by another process.

stream = new FileStream(filename, FileMode.Open, FileAccess.Read,
                                               FileShare.Read);
                       // Total bytes to read:
                       long bytesToRead = stream.Length;
                       Response.ContentType = "application/msword";
                       Response.AddHeader("Content-Disposition", "attachment; filename=" + strFileName);
                       // Read the bytes from the stream in small portions.
                       while (bytesToRead > 0)
                       {
                           // Make sure the client is still connected.
                           if (Response.IsClientConnected)
                           {
                               // Read the data into the buffer and write into the
                               // output stream.
                               byte[] buffer = new Byte[10000];
                               int length = stream.Read(buffer, 0, 10000);
                               Response.OutputStream.Write(buffer, 0, length);
                               Response.Flush();
                               // We have already read some bytes.. need to read
                               // only the remaining.
                               bytesToRead = bytesToRead - length;
                           }
                           else
                           {
                               // Get out of the loop, if user is not connected anymore..
                               bytesToRead = -1;
                           }
                       }
                   }
                   catch (Exception ex)
                   {
                       Response.Write(ex.Message);
                       // An error occurred..
                   }
                   finally
                   {
                       if (stream != null)
                       {
                           stream.Close();
                           stream.Dispose();
                       }
                   }
               }


           }