SQL即结构化查询语句（Structured Query LangUage）
但是对于创建对象来说sql语句不够用不方便所以有了Orm

ORM对象关系映射（Object Relational Mapping）
那么C#如何使用ROM呢

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using NHibernate;
using FluentNHibernate.Cfg;
using FluentNHibernate.Cfg.Db;

namespace ArpgDatabase
{
    public class NHibernateHelper
    {
        private static ISessionFactory sessionFactory = null;

        private static void InitializeSessionFactory()
        {
            //定义数据库对象（服务器地址，数据库名字，账号，密码）
            sessionFactory = Fluently.Configure()
            .Database(MySQLConfiguration.Standard.ConnectionString(db => db
           .Server("127.0.0.1")
           .Database("fourthmonthwork")
           .Username("root")
           .Password("1001")))
            .Mappings(m => m.FluentMappings.AddFromAssemblyOf<NHibernateHelper>())
            .ExposeConfiguration(e => e.Properties.Add("hbm2ddl.keywords", "none"))
            .BuildSessionFactory();
        }

        private static ISessionFactory SessionFactory
        {
            //类似于单利有且只有一个 InitializeSessionFactory();
            get
            {
                if (sessionFactory == null)
                    InitializeSessionFactory();

                return sessionFactory;
            }
        }
        /// <summary>
        /// 多条sql语句可以通过ISession来操作
        /// </summary>
        /// <returns></returns>
        public static ISession OpenSession()
        {
            return SessionFactory.OpenSession();
        }
    }
}

通过OpenSession方法提供一个ISession 对象共外界使用操作数据库

using ArpgDatabase;
using NHibernate;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace WWWServer0504
{
    public class DBAccountController
    {
        private static DBAccountController instance;
        public static DBAccountController Instance
        {
            get
            {
                if (instance == null)
                    instance = new DBAccountController();
                return instance;
            }
        }

        public Account SelectAccount(string name)
        {
            ISession session = NHibernateHelper.OpenSession();
            IList<Account> list = session.QueryOver<Account>().Where(x => x.username == name).List();
            if (list.Count > 0)
                return list[0];
            return null;
        }

        public void InsertAccount(string name , string pwd)
        {
            ISession session = NHibernateHelper.OpenSession();
            Account acc = new Account();
            acc.username = name;
            acc.password = pwd;
            session.Save(acc);
        }
    }
}

using FluentNHibernate.Mapping;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace WWWServer0504
{
    public class AccountMap : ClassMap<Account>
    {
        public AccountMap()
        {
            Table("account");
            Id(x => x.id).Column("id");
            Map(x => x.username).Column("username");
            Map(x => x.password).Column("pwd");
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace WWWServer0504
{
    public class Account
    {
        public virtual int id { get; set; }
        public virtual string username { get; set; }
        public virtual string password { get; set; }
    }
}

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