EmitMapper的使用小结

浏览数：35 / 时间：2015年06月11日

最近公司开发项目前端使用一个js框架，后端使用ef，js前台读取的json采用实体的dto来进行生成。

在网上看到了EmitMapper相对其他映射框架处理速度可以更快，就拿来用了。下面是代码中常用的几个块。

1.普通的映射。

    public class UserInfo
    {
        public int id { get; set; }
        public string name { get; set; }
        public string address { get; set; }
    }

    public class UserInfoDTO
    {        
        public string name { get; set; }
        public string address { get; set; }
    }

    var mapper = ObjectMapperManager.DefaultInstance.GetMapper<UserInfo, UserInfoDTO>();
    UserInfoDTO userdto = mapper.Map(user);

2.有外键关联，需要映射出外键所带名字

    public class UserInfo
    {
        public int id { get; set; }
        public string name { get; set; }
        public string address { get; set; }

        public Teacher teacher { get; set; }
    }
    public class Teacher
    {
        public int id { get; set; }
        public string name { get; set; }
    }
    public class UserInfoDTO
    {
        public int id { get; set; }
        public string name { get; set; }
        public string teacher { get; set; }
    }

    var user = new UserInfo { 
                id = 12, 
                name = "张三", 
                address = "北京",
                teacher = new Teacher { 
                    id = 11, 
                    name = "王五" 
                }
            };

     var mapper = ObjectMapperManager.DefaultInstance.GetMapper<UserInfo, UserInfoDTO>(
                new DefaultMapConfig()
                .ConvertUsing<Teacher, string>(t => t.name)
                );
     UserInfoDTO userdto = mapper.Map(user);

3.两个实体之间名字不一致，需要映射。

    public class UserInfo
    {
        public int id { get; set; }
        public string name { get; set; }
        public string address { get; set; }
    }
    public class UserInfoDTO
    {
        public int id { get; set; }
        public string name { get; set; }
        public string userAddress { get; set; }
    }
    var mapper = ObjectMapperManager.DefaultInstance.GetMapper<UserInfo, UserInfoDTO>(
                new DefaultMapConfig()
                .MatchMembers((x, y) =>
                {
                    if (x == "address" && y == "userAddress")
                    {
                        return true;
                    }
                    return x == y;
                })
                );
    UserInfoDTO userdto = mapper.Map(user);

4.需要对某一个字段进行特殊处理

    public class UserInfo
    {
        public int id { get; set; }
        public string name { get; set; }
        public string address { get; set; }
    }
    public class UserInfoDTO
    {
        public string id { get; set; }
        public string name { get; set; }
        public string userAddress { get; set; }
        public string userJson { get; set; }
    }
    var user = new UserInfo { 
                id = 12, 
                name = "张三", 
                address = "北京"
            };

    var mapper = ObjectMapperManager.DefaultInstance.GetMapper<UserInfo, UserInfoDTO>(
                new DefaultMapConfig()
                .PostProcess<UserInfoDTO>((value, state) =>
                {
                    //在id编号前加上今年的年份
                    value.id = DateTime.Now.ToString("yyyy") + value.id;
                    //实体的json格式
                    value.userJson = "{\"id\":\"" + value.id + "\",\"name\":\"" + value.name + "\"}";
                    return value;
                })
            );
     UserInfoDTO userdto = mapper.Map(user);

5.忽略掉某个字段的映射

    public class UserInfo
    {
        public int id { get; set; }
        public string name { get; set; }
        public string address { get; set; }
    }
    public class UserInfoDTO
    {
        public string id { get; set; }
        public string name { get; set; }
        public string address { get; set; }
    }
    var user = new UserInfo { 
                id = 12, 
                name = "张三", 
                address = "北京"
            };

    var mapper = ObjectMapperManager.DefaultInstance.GetMapper<UserInfo, UserInfoDTO>(
                new DefaultMapConfig()
                .IgnoreMembers<UserInfo, UserInfoDTO>(new string[] { "name" })
            );
    UserInfoDTO userdto = mapper.Map(user);

6.给空元素赋默认值

    public class UserInfo
    {
        public int id { get; set; }
        public string name { get; set; }
        public string address { get; set; }
        public DateTime? godate { get; set; }
    }
    public class UserInfoDTO
    {
        public string id { get; set; }
        public string name { get; set; }
        public string address { get; set; }
        public DateTime godate { get; set; }
    }
    var user = new UserInfo { 
                id = 12, 
                name = "张三", 
                address = null,
                godate = null
            };

    var mapper = ObjectMapperManager.DefaultInstance.GetMapper<UserInfo, UserInfoDTO>(
                new DefaultMapConfig()
                //如果日期为空设置为当前时间
                .NullSubstitution<DateTime?, DateTime>((value) => DateTime.Now)
                //如果string类型为null赋值为“”
                .NullSubstitution<string, string>((value) => "")
            );
    UserInfoDTO userdto = mapper.Map(user);