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=attendent;User ID=sa;Password=gemini"].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();
                           }

string conString = ConfigurationManager.ConnectionStrings["Data Source=HEIZ-PC\\SQLEXPRESSR2;Initial Catalog=attendent;User ID=sa;Password=gemini"].ConnectionString;