万能DBHelper.cs类实现数据库连接管理

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)   
            {