Object reference not set to an instance of an object

string[] content = System.IO.File.ReadAllLines(e.FullPath);
                        foreach (string line in content)
                        {
                            string[] arr;
                            arr = line.Split(','); //splitting the line which was read by the stream reader object
                            DataRow row = table.NewRow();
                            row["L_DateTime"] = DateTime.Parse(arr[0].Substring(0, 4) + "-" + arr[0].Substring(4, 2) + "-" + arr[0].Substring(6));
                            row["L_Direction"] = arr[1];
                            row["L_CardID"] = arr[2];
                            row["L_GateID"] = Convert.ToInt32(arr[3]);
                            table.Rows.Add(row);
                            i2++;
                        }

                        //Connect to DB
                        string conString = ConfigurationManager.ConnectionStrings["Data Source=HEIZ-PC\\SQLEXPRESSR2;Initial Catalog=attandent;User ID=sa;Password=pwd"].ConnectionString;
                        using (SqlConnection con = new SqlConnection(conString))
                        {
                            con.Open();
                            try
                            {
                                //Execute the command to make a temp table
                                SqlCommand cmd = new SqlCommand(tmpTable, con);
                                cmd.ExecuteNonQuery();

                                //BulkCopy the data in the DataTable to the temp table
                                using (SqlBulkCopy bulk = new SqlBulkCopy(con))
                                {
                                    bulk.DestinationTableName = "#templogDetail";
                                    bulk.WriteToServer(table);
                                }

                                //Now use the merge command to upsert from the temp table to the production table
                                string mergeSql = "merge into logDetail as Target using #templogDetail as Source on" +
                                                "Target.L_DateTime=Source.L_DateTime, Target.L_Direction=Source.L_Direction," +
                                                    "Target.L_CardID=Source.L_CardID, when matched then update set Target.L_GateID=Source.L_GateID," +
                                                        "when not matched then insert (L_DateTime,L_Direction,L_CardID,L_GateID)" +
                                                            "values (Source.L_DateTime,Source.L_Direction,Source.L_CardID,Source.L_GateID);";

                                cmd.CommandText = mergeSql;
                                cmd.ExecuteNonQuery();

                                //Clean up the temp table
                                cmd.CommandText = "drop table #templogDetail";
                                cmd.ExecuteNonQuery();
                            }