求SQLHelper类中文版（注释中文的）

using System;
using System.Collections.Generic;
using System.Text;
using System.Data.SqlClient;
using System.Data;
using System.Configuration;
using BookShop.Models;

namespace BookShop.DAL
{
public class DBHelp
{
public static SqlConnection connection;
public static SqlConnection Connection
{
get
{
string connectionString = ConfigurationManager.ConnectionStrings["mybookshop"].ConnectionString;
if (connection == null)
{
connection = new SqlConnection(connectionString);
connection.Open();
}
else if (connection.State == System.Data.ConnectionState.Closed)
{
connection = new SqlConnection(connectionString);
connection.Op