Cannot access a disposed object. Object name: System.Net.Sockets.NetworkStream

try {
   string strConn = ConfigurationManager.ConnectionStrings["Connection"].ConnectionString.ToString();
   SqlConnection con = new SqlConnection(strConn);
 
   FtpWebRequest request = (FtpWebRequest)WebRequest.Create("ftpserver");
 
   request.Credentials = new NetworkCredential("username", "pass");
 
   FtpWebResponse response = (FtpWebResponse)request.GetResponse();
   Stream responsestream = response.GetResponseStream();
   StreamReader sr = new StreamReader(responsestream);
 
   string line = sr.ReadLine();
   string[] value = line.Split(',');
   DataTable dt = new DataTable();
   DataRow row;
   foreach (string dc in value) {
      dt.Columns.Add(new DataColumn(dc));
   }
 
   while (!sr.EndOfStream) {
      value = sr.ReadLine().Split(',');
      if (value.Length == dt.Columns.Count) {
         row = dt.NewRow();
         row.ItemArray = value;
         dt.Rows.Add(row);
      }
   }
 
   SqlBulkCopy bc = new SqlBulkCopy(con.ConnectionString, SqlBulkCopyOptions.TableLock);
   bc.DestinationTableName = "CSVTest";
   bc.BatchSize = dt.Rows.Count;
   con.Open();
   bc.WriteToServer(dt);
   bc.Close();
   con.Close();
   sr.Close();
   sr.Dispose();
   //File.Open(str1, FileMode.Open, FileAccess.Read, FileShare.None); 
   using (var writer = new StreamWriter(responsestream)) {
      writer.Write("");
   }
}
catch (ObjectDisposedException a) {
   Console.WriteLine("Caught: {0}", a.Message);
}
finally {
}

read file from ftp sever complete read file while loop thorws error

Cannot access a disposed object.
Object name: 'System.Net.Sockets.NetworkStream'.