c# automapper 使用(一)

一、最简单的用法

有两个类User和UserDto

    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
    }

    public class UserDto
    {
        public string Name { get; set; }
        public int Age { get; set; }
    }

将User转换成UserDto也和简单

    Mapper.Initialize(x => x.CreateMap<User, UserDto>());
    User user = new User()
    {
        Id = 1,
        Name = "caoyc",
        Age = 20
    };
    var dto = Mapper.Map<UserDto>(user);

 这是一种最简单的使用，AutoMapper会更加字段名称去自动对于，忽略大小写。

二、如果属性名称不同

将UserDto的Name属性改成Name2

    Mapper.Initialize(x => 
        x.CreateMap<User, UserDto>()
         .ForMember(d =>d.Name2, opt => {
            opt.MapFrom(s => s.Name);
            })
        );

    User user = new User()
    {
        Id = 1,
        Name = "caoyc",
        Age = 20
    };

    var dto = Mapper.Map<UserDto>(user);

三、使用Profile配置

自定义一个UserProfile类继承Profile，并重写Configure方法

    public class UserProfile : Profile
    {
        protected override void Configure()
        {
            CreateMap<User, UserDto>()
                .ForMember(d => d.Name2, opt =>
                {
                    opt.MapFrom(s => s.Name);
                });
        }
    }

使用时就这样

    Mapper.Initialize(x => x.AddProfile<UserProfile>());

    User user = new User()
    {
        Id = 1,
        Name = "caoyc",
        Age = 20
    };

    var dto = Mapper.Map<UserDto>(user);

四、空值替换NullSubstitute

空值替换允许我们将Source对象中的空值在转换为Destination的值的时候，使用指定的值来替换空值。

    public class UserProfile : Profile
    {
        protected override void Configure()
        {
            CreateMap<User, UserDto>()
                .ForMember(d => d.Name2, opt => opt.MapFrom(s => s.Name))
                .ForMember(d => d.Name2, opt => opt.NullSubstitute("值为空"));
                
        }
    }

    Mapper.Initialize(x => x.AddProfile<UserProfile>());

    User user = new User()
    {
        Id = 1,
        Age = 20
    };

    var dto = Mapper.Map<UserDto>(user);

结果为：

五、忽略属性Ignore

    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
    }

    public class UserDto
    {
        public string Name { get; set; }
        public int Age { get; set; }

    }

    public class UserProfile : Profile
    {
        protected override void Configure()
        {
            CreateMap<User, UserDto>().ForMember("Name", opt => opt.Ignore());
        }
    }

使用

    Mapper.Initialize(x => x.AddProfile<UserProfile>());

    User user = new User()
    {
        Id = 1,
        Name="caoyc",
        Age = 20
    };

    var dto = Mapper.Map<UserDto>(user);

结果：

六、预设值

如果目标属性多于源属性，可以进行预设值

    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
    }

    public class UserDto
    {
        public string Name { get; set; }
        public int Age { get; set; }
        public string Gender { get; set; }

    }

    public class UserProfile : Profile
    {
        protected override void Configure()
        {
            CreateMap<User, UserDto>();
        }
    }

使用

    Mapper.Initialize(x => x.AddProfile<UserProfile>());

    User user = new User()
    {
        Id = 1,
        Name="caoyc",
        Age = 20
    };

    UserDto dto = new UserDto() {Gender = "男"};
    Mapper.Map(user, dto);

 七、类型转换ITypeConverter

如果数据中Gender存储的int类型，而DTO中Gender是String类型

    public class User
    {
        public int Gender { get; set; }
    }

    public class UserDto
    {
        public string Gender { get; set; }
    }

类型转换类，需要实现接口ITypeConverter

    public class GenderTypeConvertert : ITypeConverter<int, string>
    {
        public string Convert(int source, string destination, ResolutionContext context)
        {
            switch (source)
            {
                case 0:
                    destination = "男";
                    break;
                case 1:
                    destination = "女";
                    break;
                default:
                    destination = "未知";
                    break;
            }
            return destination;
        }
    }

配置规则

    public class UserProfile : Profile
    {
        protected override void Configure()
        {
            CreateMap<User, UserDto>();

            CreateMap<int, string>().ConvertUsing<GenderTypeConvertert>();
            //也可以写这样
            //CreateMap<int, string>().ConvertUsing(new GenderTypeConvertert());
        }
    }

使用

    Mapper.Initialize(x => x.AddProfile<UserProfile>());

    User user0 = new User() { Gender = 0 };
    User user1 = new User() { Gender = 1 };
    User user2 = new User() { Gender = 2 };
    var dto0= Mapper.Map<UserDto>(user0);
    var dto1 = Mapper.Map<UserDto>(user1);
    var dto2 = Mapper.Map<UserDto>(user2);

    Console.WriteLine("dto0:{0}", dto0.Gender);
    Console.WriteLine("dto1:{0}", dto1.Gender);
    Console.WriteLine("dto2:{0}", dto2.Gender);

结果

八、条件约束Condition

当满足条件时才进行映射字段，例如人类年龄，假设我们现在人类年龄范围为0-200岁（这只是假设），只有满足在这个条件才进行映射

DTO和Entity

    public class User
    {
        public int Age { get; set; }
    }

    public class UserDto
    {
        public int Age { get; set; }
    }

Profile

    public class UserProfile : Profile
    {
        protected override void Configure()
        {
            CreateMap<User, UserDto>().ForMember(dest=>dest.Age,opt=>opt.Condition(src=>src.Age>=0 && src.Age<=200));
        }
    }

使用代码

    Mapper.Initialize(x => x.AddProfile<UserProfile>());

    User user0 = new User() { Age = 1 };
    User user1 = new User() { Age = 150 };
    User user2 = new User() { Age = 201 };
    var dto0= Mapper.Map<UserDto>(user0);
    var dto1 = Mapper.Map<UserDto>(user1);
    var dto2 = Mapper.Map<UserDto>(user2);

    Console.WriteLine("dto0:{0}", dto0.Age);
    Console.WriteLine("dto1:{0}", dto1.Age);
    Console.WriteLine("dto2:{0}", dto2.Age);

输出结果