Automapper 中的条件属性映射不起作用

Question

我正在使用 Automapper 6.2.0，并且我有以下类：

public class User
{
    public Address Address { get; set; }
}

public class Address
{
    public string Street { get; set; }
}

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

我的映射配置如下：

        CreateMap<UserDto, User>()
            .ForPath(dest => dest.Address.Street, opt => opt.Condition(cond => !string.IsNullOrEmpty(cond.Source.AddressStreet)))
            .ForPath(dest => dest.Address.Street, opt => opt.MapFrom(src => src.AddressStreet));

我像这样将 UserDto 映射到 User：

var userDto = new UserDto{ AddressStreet = null };
var user = mapper.Map<User>(userDto);
var address = user.Address;//I expect the prop to be null, since the mapping condition is not met...

这会生成一个 user.Address 对象实例，其中 Street 设置为 null。我宁愿 user.Address 根本不被实例化。

Answer 1

您的映射配置引发以下异常。

System.ArgumentException occurred
HResult=0x80070057
Message=Expression 'dest => dest.Address.Street' must resolve to top-
level member and not any child object's properties. You can use 
ForPath, a custom resolver on the child type or the AfterMap option 
instead.
Source=<Cannot evaluate the exception source>
StackTrace:
at AutoMapper.Internal.ReflectionHelper.FindProperty(LambdaExpression 
lambdaExpression)
at AutoMapper.Configuration.MappingExpression`2.ForMember[TMember]
(Expression`1 destinationMember, Action`1 memberOptions)
at NetCore.AutoMapperProfile..ctor()

请尝试以下映射配置：

CreateMap<UserDto, User>()
.ForMember(dest => dest.Address, opt => opt.Condition(src => !string.IsNullOrEmpty(src.AddressStreet)))
.ForMember(dest => dest.Address, opt => opt.MapFrom(src => src.AddressStreet));

以上将导致user.Address = null