Automapper nested mapping

It lacks the mapping from Address to CompanyInformationDTO, as those objects are on the same nest-level.

The map is created for MatchCompanyRequest -> MatchCompanyRequestDTO, but it is unable to figure out whether it can map Address to CompanyInformationDTO.

So your MatchCompanyRequestDTO could in fact have same declaration as your CompanyInformationDTO:

public class MatchCompanyRequestDTO
{
    public string CompanyName {get;set;}
    public AddressDTO Address {get;set;}
}

This of course only affects you if you want to use automatic mapping. You still can configure your maps manually, but it seems like the DTOs should be fixed instead, let's try anyway:

public class CustomResolver : ValueResolver<Address, CompanyInformationDTO>
{
    protected override CompanyInformationDTO ResolveCore(Address source)
    {
        return new CompanyInformationDTO() { Address = Mapper.Map<Address, AddressDTO>(source) };
    }
}
// ...

AutoMapper.Mapper.CreateMap<MatchCompanyRequest, MatchCompanyRequestDTO>()
    .ForMember(dest => dest.companyInformationDTO, opt => opt.ResolveUsing<CustomResolver>().FromMember(src => src.Address)); // here we are telling to use our custom resolver that converts Address into CompanyInformationDTO

The important thing is you define how deeper is your navigation, to previne the stackoverflow problems. Imagine this possibility:

You have 2 entities Users and Notifications in NxN model (And you have DTOs object to represent that), when you user auto mapper without set MaxDepth in you mapper expression, "Houston we have a problem" :).

The code below show a workaround to resolve this for all Mappers. If you want can be defined to each mapper. Like this Question

Solution 1 (Global Definition)

public class AutoMapperConfig
{
    public static void RegisterMappings()
    {
        Mapper.Initialize(mapperConfiguration =>
        {
            mapperConfiguration.AddProfile<DomainModelToYourDTOsMappingProfile>();
            mapperConfiguration.AddProfile<YourDTOsToDomainModelMappingProfile>();
            mapperConfiguration.AllowNullCollections = true;
            mapperConfiguration.ForAllMaps(
                (mapType, mapperExpression) => {
                    mapperExpression.MaxDepth(1);
                });
        }
    }

Solution 2 (For each Mapper)

 public class AutoMapperConfig
 {
     public static void RegisterMappings()
     {
         Mapper.CreateMap<User, DTOsModel>()
               .MaxDepth(1);
     }
 }