Automapper AutoMapper.AutoMapperMappingException: Error mapping types

Question

I am getting a peculiar error with Automapper

Error messages:

Mapping types:
TransportOffer -> TransportOfferDto
Model.TransportOffer -> Dto.TransportOfferDto

Type Map configuration:
TransportOffer -> TransportOfferDto
Model.TransportOffer -> Dto.TransportOfferDto

Property:
FromCity ---> AutoMapper.AutoMapperMappingException: Error mapping types.

Mapping types:
City -> CityDto
Model.City -> Dto.CityDto

Type Map configuration:
City -> CityDto
Model.City -> Dto.CityDto

Property:
Country ---> System.TypeLoadException: Method 'Add' in type 'Proxy_System.Collections.Generic.ICollection`1[[Dto.CountryDto, BusinessLogic, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]__17474517' from assembly 'AutoMapper.Proxies, Version=0.0.0.0, Culture=neutral, PublicKeyToken=be96cd2c38ef1005' does not have an implementation.

Below are my entities and DTO and the query that retrieves the data. I am using Automapper 7.0.1 and Automapper.Attributes 6.0.1

I have tried also with custom mapping configuration and the error is the same.

Here is the Automapper custom property configuration:

Mapper.Initialize
(
    config =>
    {
        config.CreateMap<TransportOfferDto, TransportOffer>()
            .ForMember(dest => dest.FromCity, conf => conf.MapFrom(src => src.FromCity))
            .ForMember(dest => dest.FromCountry, conf => conf.MapFrom(src => src.FromCountry))
            .ForMember(dest => dest.ToCity, conf => conf.MapFrom(src => src.ToCity))
            .ForMember(dest => dest.ToCountry, conf => conf.MapFrom(src => src.ToCountry));
         }
     );

Country - entity:

public class Country : BaseEntity<Int32>
{        
    public string Name { get; set; }
    public string Code { get; set; }
    public string Capital { get; set; }
    public Int32 TotalSold { get; set; }
}

CountryDto

[MapsTo(typeof(Country))]
[MapsFrom(typeof(Country))]
public class CountryDto : EntityDto<Int32>
{
    public string Name { get; set; }
    public string Code { get; set; }
    public string Capital { get; set; }
    public Int32 TotalSold { get; set; }
}

City - entity:

public class City : BaseEntity<Int32>
{        
    public string Name { get; set; }
    public Int32 CountryID { get; set; }
    public virtual Country Country { get; set; }
}

CityDto

[MapsTo(typeof(City))]
[MapsFrom(typeof(City))]
public class CityDto : EntityDto<Int32>
{
    public Int32 CountryID { get; set; }
    public virtual ICollection<CountryDto> Country { get; set; }

    public string Name { get; set; }

}

TransportOffer - entity:

public class TransportOffer : BaseEntity<Guid>
{
    public Guid TransportToken { get; set; }
    public DateTime Date { get; set; }
    public Int32 FromCityID { get; set; }
    public  virtual City FromCity { get; set; }
    public Int32 FromCountryID { get; set; }
    public virtual Country FromCountry { get; set; }
    public Int32 ToCityID { get; set; }
    public virtual City ToCity { get; set; }
    public Int32 ToCountryID { get; set; }
    public virtual Country ToCountry { get; set; }
}

TransportOfferDto:

[MapsTo(typeof(TransportOffer))]
[MapsFrom(typeof(TransportOffer))]
public class TransportOfferDto : EntityDto<Guid>
{
    public Guid TransportToken { get; set; }
    public DateTime Date { get; set; }    
    public Int32 FromCityID { get; set; }
    public virtual CityDto FromCity { get; set; }       
    public Int32 FromCountryID { get; set; }
    public virtual CountryDto FromCountry { get; set; } 
    public Int32 ToCityID { get; set; }
    public virtual CityDto ToCity { get; set; }
    public Int32 ToCountryID { get; set; }
    public virtual Country ToCountry { get; set; }
} 

Query

var query = Repository.GetAll()
            .Include(x => x.FromCountry)
            .Include(x => x.FromCity)
            .Include(x => x.ToCountry)
            .Include(x => x.ToCity)
            .Where(p => p.MembershipID == input).ToList();

return ObjectMapper.Map<List<TransportOfferDto>>(query);

Solution

Your CityDto class has a collection of Countries

[MapsTo(typeof(City))] [MapsFrom(typeof(City))] 
public class CityDto : EntityDto<Int32> 
{ 
    public Int32 CountryID { get; set; }
    public virtual ICollection<CountryDto> Country { get; set; } 
    public string Name { get; set; } 
}

But your City class has a single Country.

public class City : BaseEntity<Int32>
{        
    public string Name { get; set; }
    public Int32 CountryID { get; set; }
    public virtual Country Country { get; set; }
}

How are you mapping them?

Comments

[V0ldek]

You probably need to show us the remaining DTOs as well.

[Mel Gerats]

Did you create a mapping for Country and City?

[Lucian Bargaoanu]

I'm guessing you have somewhere a map for ICollection :)

[Martin Spasovski]

@V0ldek - that is the complete DTO it is a mapping table.

[Martin Spasovski]

@MelGerats - The mapping for country and city is made the same way as MapsFrom/MapsTo with automapper attributes

[Martin Spasovski]

@LucianBargaoanu - No I dont have mapping for ICollection

[Mel Gerats]

public virtual ICollection<CountryDto> you do

[Martin Spasovski]

@MelGerats - Yes you're right, I forgot, Do i need to add specific ICollection mapping in the automapper configuration?

[V0ldek]

You don't, Automapper is smart enough to map an ICollection<From> to an ICollection<To>. But it won't automatically map an object to a collection of objects, see Mel Gerats answer.

[Martin Spasovski]

I am not mapping them anyhow I think that the DTO it should be without the ICollection??!!

[Mel Gerats]

I think so too!

[Martin Spasovski]

Got it working, the ICollection was the problem, it somehow got c/p from another class... Thank you all.

[Lucian Bargaoanu]

And you actually have an ICollection map. That happens because CreateMissingTypeMaps is true. Setting it to false would make things easier to understand.