如何映射到构造函数参数而不是属性设置器

使用 ConstructUsing

这将允许您指定在映射期间使用哪个构造函数。但是所有其他属性都将根据约定自动映射。

还要注意,这与 ConvertUsing 在这种情况下,convert-using将不会继续通过约定进行映射,而是让您完全控制映射。

Mapper.CreateMap<ObjectFrom, ObjectTo>()
    .ConstructUsing(x => new ObjectTo(arg0, arg1, etc));

using AutoMapper;
using NUnit.Framework;

namespace UnitTests
{
    [TestFixture]
    public class Tester
    {
        [Test]
        public void Test_ConstructUsing()
        {
            Mapper.CreateMap<ObjectFrom, ObjectTo>()
                .ConstructUsing(x => new ObjectTo(x.Name));

            var from = new ObjectFrom { Name = "Jon", Age = 25 };

            ObjectTo to = Mapper.Map<ObjectFrom, ObjectTo>(from);

            Assert.That(to.Name, Is.EqualTo(from.Name));
            Assert.That(to.Age, Is.EqualTo(from.Age));
        }
    }

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

    public class ObjectTo
    {
        private readonly string _name;

        public ObjectTo(string name)
        {
            _name = name;
        }

        public string Name
        {
            get { return _name; }
        }

        public int Age { get; set; }
    }
}

最佳实践是使用AutoMapper提供的有文档记录的方法 http://docs.automapper.org/en/stable/Construction.html

public class SourceDto
{
        public SourceDto(int valueParamSomeOtherName)
        {
            Value = valueParamSomeOtherName;
        }

        public int Value { get; }
}

Mapper.Initialize(cfg => cfg.CreateMap<Source, SourceDto>().ForCtorParam("valueParamSomeOtherName", opt => opt.MapFrom(src => src.Value)));

你应该使用 Map

Mapper.CreateMap<ObjectFrom, ObjectTo>()

var from = new ObjectFrom { Name = "Jon", Age = 25 };

var to = Mapper.Map(from, new ObjectTo(param1));

在写这个答案的时候,AutoMapper会自动完成(用一个简单的 CreateMap<>() .ConstructUsing(...) 是一条路要走。

public class PersonViewModel
{
    public int Id { get; set; }

    public string Name { get; set; }
}

public class Person
{
    public Person (int id, string name)
    {
        Id = id;
        Name = name;
    }

    public int Id { get; }

    public string Name { get; }
}

public class PersonProfile : Profile
{
    public PersonProfile()
    {
        CreateMap<PersonViewModel, Person>();
    }
}

注意:这假设您正在使用 Profiles

如下所示使用时,将生成正确的对象:

var model = new PersonViewModel
{
    Id = 1
    Name = "John Smith"
}

// will correctly call the (id, name) constructor of Person
_mapper.Map<Person>(model);

wiki on GitHub

就我个人而言,在使用AutoMapper时,我总是希望尽可能明确,以避免将来出现任何潜在的错误。

如果你打电话给 ConstructUsing

如果开发人员反转2个字符串参数或在一些现有可选参数之前添加一个新的可选参数,该怎么办?如果某个属性没有映射到它应该映射的目标属性,则会出现映射错误。

这是不同的签名 施工 方法:

TMappingExpression ConstructUsing(Func<TSource, ResolutionContext, TDestination> ctor);
TMappingExpression ConstructUsing(Expression<Func<TSource, TDestination>> ctor);

an expression tree may not contain a named argument specification ).

 CreateMap<FromType, ToType>()
    .ConstructUsing((src, res) =>
    {
        return new ToType(
            foo: src.MyFoo,
            bar: res.Mapper.Map<BarModel>(src.MyBar),
        );
    });

注意Func的第二个参数 res Resolution Context . 此参数允许您使用已注册的映射。

private set Map 方法:

TDestination Map<TSource, TDestination>(TSource source, TDestination destination);

mapper.Map(updateModel, existingEntity);
await dbContext.SaveChangesAsync();

谢天谢地还有 another way to update entities with EF Core .