在 Automapper 配置中使用 appsettings.json 值

Question

在 Automapper 中映射两个对象时，有没有办法从 appsettings.json 获取值？

public class MapperProfile : Profile
{
     public MapperProfile()
     {
          CreateMap<Employee, EmployeeDto>()
             .ForMember(employeeDto => employeeDto.Picture, employee => employee.MapFrom(employee => $"{someValueFromAppSettings}{employee.Picture}"
     }
}

我需要在映射的图片名称前附加路径，但我似乎无法弄清楚如何以及是否可以使用 Automapper。

Answer 1

来自 AutoMapper 文档：

You can’t inject dependencies into Profile classes.

但是（至少）有两种方法可以实现您想要的：

使用IValueResolver<in TSource, in TDestination, TDestMember>界面。

public class EmployeeDtoPathResolver: IValueResolver<Employee, EmployeeDto, string>
    {
        private readonly IConfiguration _configuration
        public CarBrandResolver(IConfiguration configuration)
        {
            _configuration= configuration;
        }

        public string Resolve(Employee source, EmployeeDto destination, int destMember, ResolutionContext context)
        {
            var path = // get the required path from _configuration;
            return $"{path}{source.Picture}"
        }
    }

public class MapperProfile : Profile
{
     public MapperProfile()
     {
          CreateMap<Employee, EmployeeDto>()
             .ForMember(employeeDto => employeeDto.Picture, opt => opt.MapFrom<EmployeeDtoPathResolver>()); // Edited this
     }
}

使用 IMappingAction<in TSource, in TDestination> 实施。

它基本上是将 Before 和 After Map Actions 封装成可重复使用的小型类.

public class EmployeeDtoAction : IMappingAction<Employee, EmployeeDto>
{
    private readonly IConfiguration _configuration;

    public EmployeeAction (IConfiguration configuration)
    {
        _configuration = configuration ?? throw new ArgumentNullException(nameof(configuration));
    }

    public void Process(Employee source, EmployeeDto destination, ResolutionContext context)
    {
        var path =  // get the required path from _configuration;
        destination.Picture = $"{path}{destination.Picture}"
    }
}

public class MapperProfile : Profile
{
     public MapperProfile()
     {
          CreateMap<Employee, EmployeeDto>()
             .AfterMap<EmployeeDtoAction>(); // Added this
     }
}

在 Automapper 配置中使用 appsettings.json 值

Using appsettings.json values in Automapper configuration

.net

c#

automapper