SqlDBHelper.cs: 数据库连接与执行命令

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.Open();
                }
                else if (connection.State == System.Data.ConnectionState.Broken)

                {
                    connection.Close();
                    connection.Open();
                }
                return connection;
            }
        }
        



        #region 增，删，改ExecuteNonQuery
        /// <summary>
        /// 单个数据增，删，改
        /// </summary>
        /// <param name="safeSql"></param>
        /// <returns></returns>
        public static int ExecuteCommand(string safeSql)
        {
            try
            {
                using (SqlCommand cmd = new SqlCommand(safeSql, Connection))
                {
                    int result = cmd.ExecuteNonQuery();
                    return result;
                }

            }
            catch (SqlException ex)
            {