一、什么是automapper?

automapper是一个简单的对象映射框架(oom)，将一个对象映射到另一个对象。

二、automapper的好处

以前的时候我们将dto对象转换为model对象时,我们必须将每一个属性都手动映射

实体类

    /// <summary>
    /// 用户表
    /// </summary>
    [table("tb_user")]
    public class tbuser
    {
        /// <summary>
        /// 用户id
        /// </summary>
        [key]
        [column("userid")]
        [stringlength(32)]
        public string userid { get; set; }
        /// <summary>
        /// 用户名
        /// </summary>
        [column("username")]
        [stringlength(20)]
        public string username { get; set; }
        /// <summary>
        /// 邮箱
        /// </summary>
        [column("email")]
        [stringlength(30)]
        public string email { get; set; }
        /// <summary>
        /// 添加时间
        /// </summary>
        [column("addtime")]
        [required]
        public datetime addtime { set; get; }
    }

dto传输对象

    /// <summary>
    /// 用户传输对象
    /// </summary>
    public class userdto
    { 
        /// <summary>
        /// 用户id
        /// </summary>
        [stringlength(32, errormessage = "{0}最多{1}个字符"), display(name = "用户id")]
        public string userid { get; set; }
        /// <summary>
        /// 用户名
        /// </summary>
        [stringlength(20, errormessage = "{0}最多{1}个字符"), display(name = "用户名")]
        public string username { get; set; }
        /// <summary>
        /// 邮箱
        /// </summary>
        [stringlength(30, errormessage = "{0}最多{1}个字符"), display(name = "邮箱")]
        public string email { get; set; }
    }

业务层

    /// <summary>
    /// 业务处理
    /// </summary>
    public class userservice : iuserservice
    {
        private readonly mydbcontext _dbcontext;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="dbcontext"></param>
        public userservice(mydbcontext dbcontext)
        {
            _dbcontext = dbcontext;
        }
        /// <summary>
        /// 添加用户
        /// </summary>
        /// <param name="dto">实体传输对象</param>
        /// <returns></returns>
        public int add(userdto dto)
        {
            var user = new tbuser
            {
                userid = guid.newguid().tostring("n"),
                email = dto.email,
                username = dto.username,
                addtime = datetime.now
            };
            _dbcontext.add(user);
            return _dbcontext.savechanges();
        }
        /// <summary>
        /// 编辑用户信息
        /// </summary>
        /// <param name="dto">实体传输对象</param>
        /// <returns></returns>
        public int update(userdto dto)
        {
            var user = _dbcontext.tbusers.find(dto.userid);
            if(user==null) throw new exception("获取用户信息失败");
            user.username = dto.username;
            user.email = dto.email;
            return _dbcontext.savechanges();
        }
    }

这样情况还可以，属性不是很多，如果属性过多（几十，几百），还需要手动赋值，简直太头疼了，还会导致大量的时间浪费在对象转换中，用automapper，只需要简单的配置就可以完成两个对象之间的属性映射，开发中省去了属性转换的时间，从而提高工作效率。

三、使用automapper

安装引用

通过程序包管理器控制台安装automapper

install-package automapper -version 9.0.0

install-package automapper.extensions.microsoft.dependencyinjection -version 7.0.0

配置映射关系

创建一个类并继承automapper的profile类

    public class mappings : profile
    {
        public mappings()
        {
            createmap<userdto, tbuser>();
        }
    }

注入服务

            //注入automapper服务，mappings就是自己创建的映射类
            services.addautomapper(typeof(mappings));

 修改业务层代码

    /// <summary>
    /// 业务处理
    /// </summary>
    public class userservice : iuserservice
    {
        private readonly mydbcontext _dbcontext;
        /// <summary>
        /// 注入接口
        /// </summary>
        private readonly imapper _mapper;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="dbcontext"></param>
        /// <param name="mapper"></param>
        public userservice(mydbcontext dbcontext,imapper mapper)
        {
            _dbcontext = dbcontext;
            _mapper = mapper;
        }
        /// <summary>
        /// 添加用户
        /// </summary>
        /// <param name="dto">实体传输对象</param>
        /// <returns></returns>
        public int add(userdto dto)
        {
            var info = _mapper.map<userdto, tbuser>(dto);
            info.addtime=datetime.now;
            info.userid = guid.newguid().tostring("n");
            //var user = new tbuser
            //{
            //    userid = guid.newguid().tostring("n"),
            //    email = dto.email,
            //    username = dto.username,
            //    addtime = datetime.now
            //};
            _dbcontext.add(info);
            return _dbcontext.savechanges();
        }
        /// <summary>
        /// 编辑用户信息
        /// </summary>
        /// <param name="dto">实体传输对象</param>
        /// <returns></returns>
        public int update(userdto dto)
        {
            var user = _dbcontext.tbusers.find(dto.userid);
            if(user==null) throw new exception("获取用户信息失败");
            //user.username = dto.username;
            //user.email = dto.email;
            _mapper.map(dto, user);
            return _dbcontext.savechanges();
        }
    }

运行测试

 

ps：一般在使用automapper转换时dto中字段名称要跟实体对象定义一样才能转换成功。