ASP.NET Core 3.1 Web API 和 Entity Framework Core：AutoMapper 获取错误映射类型 MIssing Type mpa 配置或不支持的映射

Question

I am using Automapper to copy the content from DTO view model to an entity class but I get an error:

Error mapping types:
ViewModelDto -> Models.MyEntity
Type Map configuration:
ViewModelDto -> ViewModelDto -> Models.MyEntity
EmbeddedClass

The last section of the string is an embedded object which is the issue that is throwing the exception. It is defined in source and destination class as a collection of records.

In my incoming ViewModelDto, the embedded class is listed as

public class ViewModelDto
{
  public List<MyEntity> MyEntities {get;set;}
}

In the MyEntity class, this is autogenerated by scaffolding

public partial class MyEntity
{
    public MyEntity()
    {
        MyEntities = new HashSet<MyEntity>();
    }

    public virtual ICollection<MyEntity> MyEntities {get;set;}
}

In my MappingProfile.cs :

public MappingProfile()
{
    CreateMap<List<ViewModelDto>, List<MyEntity>>().ReverseMap();
}

When looking at both ViewModelDto and MyEntity class, the MyEntity is defined in both files. Not sure what is causing the thrown exception

Tried a few new things, in the mappingprofile.s

CreateMap<ViewModelDto, Drill>)().ForMember(dest => dest.MyEntity, opt => opt.UseDestination());
CreateMapCreateMap<List<ViewModelDto>, List<MyEntity>>)();

In my startup.cs

In the ConfigureServices(IServiceCollection services)
{
  services.AddAutoMapper(typeof(Startup));
}

Answer 1

Seems like there is a Mapping Issue between the List and HashSet, you can try this:

CreateMap<ViewModelDto, MyEntity>(MemberList.Source)
    .ForMember(dest => dest.MyEntities, opt => opt.UseDestinationValue());

With this, AutoMapper will try to use the destination value type (HashSet) instead of the origin (List).

Answer 2

Added this to my Startup.cs to resolve the issue, Need to register the MappingProfile in the Automapper Service

services.AddAutoMapper(typeof(MappingProfile));