How to get AutoMapper to use interface mappings and concrete mappings at the same time

[Shaun Smith]

I'm trying to get AutoMapper to update all properties on my object from the interface level (DRY approach) but only the interface properties are updating:

I've tried looking into and messing around with the include paths from the AutoMapper documentation but it isn't working the way I would expect and not sure if it's even relevant: https://github.com/AutoMapper/AutoMapper/wiki/Mapping-inheritance

Here are my models:

    public interface IEntity {
        int Id { get; set; }
    }


    public interface IDatedEntity : IEntity {
        DateTime DateCreated { get; set; }
        DateTime DateModified { get; set; }
    }


    public interface IBMSEntity : IDatedEntity {
        string Notes { get; set; }
        bool Active { get; set; }


    }


    public class ProjectStatus : IBMSEntity {
        public string Name { get; set; }


        public StatusType Type { get; set; }


        public bool IsDefault { get; set; }


        #region Interface Properties
        public int Id { get; set; }
        public DateTime DateCreated { get; set; }
        public DateTime DateModified { get; set; }
        public string Notes { get; set; }
        public bool Active { get; set; }
        #endregion
    }

And here is the the portion of code that accepts the IDatedEntity and maps it across for the purpose of updating using EntityFramework:

    public class BaseDatedEntityUpdate<T> : BaseEntityUpdate<T>, IUpdate<T> where T : class, IDatedEntity {


        public BaseDatedEntityUpdate(BMSContext context, IValidationDictionary validation) : base(context, validation) { }


        public override T Update(T entity) {
            //setting - I'd like to put this on the base mappings also
            var now = DateTime.Now;
            entity.DateModified = now;


            //mapping
            var original = dbSet.Find(entity.Id);
            Mapper.Map(entity, original);


            return original;
        }
    }

I have 2 options for my map configuration:

**Option 1:**

I put my ignore properties on the base type:

            //testing base/interface maps
            Mapper.CreateMap<IDatedEntity, IDatedEntity>()
                .ForMember(x => x.DateCreated, y=> {
                    y.UseDestinationValue();
                    y.Ignore();
                });


            Mapper.CreateMap<ProjectStatus, ProjectStatus>();

This will not ignore DateCreated so I have to change

Mapper.Map(entity, original);

 to

Mapper.Map<IDatedEntity, IDatedEntity>(entity, original);

but then I have the problem where my project status properties (such as Name, Type and IsDefault) are not getting mapped across.

**Option 2:** 

I put the mappings on my concrete type:

            //testing base/interface maps
            Mapper.CreateMap<IDatedEntity, IDatedEntity>();


            Mapper.CreateMap<ProjectStatus, ProjectStatus>()
                .ForMember(x => x.DateCreated, y=> {
                    y.UseDestinationValue();
                    y.Ignore();
                });

This technically works the way I want it to, but it isn't very DRY.

**Question:**

Is there a way to apply the mappings to the base type and keep my code DRY?

I.e. I want to use Option 1, whereby all ProjectStatus (and any other derivatives of IDatedEntity) properties are mapped across - without having to create detailed concrete type mappings?

I have also posted this as a question on StackOverflow at the following URL: 
http://stackoverflow.com/questions/33892416/how-to-get-automapper-to-use-interface-mappings-and-concrete-mappings

[Jimmy Bogard]

Hm, have you tried putting the IgnoreMap attribute on the interface?

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[Shaun Smith]

I don't want any of the maps to be ignored, I need both the interface maps and the derivative maps to be applied under the context of interface.

[Shaun Smith]

Sorry, I misunderstood.

Option 1 shows the ignore map on the interface, this has the problem whereby the properties on ProjectStatus do not map across.

[Jimmy Bogard]

Sorry, I meant the attribute, putting that on the properties on the interface. Then you don't have to do any sort of base interface CreateMap call.

On Nov 30, 2015, at 10:12 AM, Shaun Smith <shauns...@googlemail.com> wrote:

Sorry, I misunderstood.

Option 1 shows the ignore map on the interface, this has the problem whereby the properties on ProjectStatus do not map across.

[Shaun Smith]

I’m sorry I don’t fully understand,

 

Are you able to show me an example or pseudo code example?

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[Jimmy Bogard]

    public interface IDatedEntity : IEntity {

        [IgnoreMap]
        DateTime DateCreated { get; set; }

        [IgnoreMap]
        DateTime DateModified { get; set; }

[Shaun Smith]

Sorry Jimmy, that was ridiculously simpler than I was expecting.

 

As you can see from my code I have to use the destination value and I also wish to use other values such as mapping DateTime.Now to DateModified. Is there a way I can achieve this behaviour?

[Jimmy Bogard]

UseDestinationValue is only really used for collection types, not primitives. For collections/complex types it means "use the destination instance, but map all child properties/items". In your case, you don't need UseDestinationValue, just Ignore.

For the part where you're filling in DateTime.Now, that's a bit tougher. You can try IncludeBase on derived maps, and in the base map you include that behavior:

CreateMap<IDatedEntity, IDatedEntity>()

    .ForMember(d => d.DateModified, opt => opt.MapFrom(src => DateTime.Now));

CreateMap<DerivedEntity, DerivedEntity>()

   .IncludeBase<IDatedEntity, IDatedEntity>();

Or you can also try conventions, new in 4.1 https://github.com/AutoMapper/AutoMapper/wiki/Conventions

[Shaun Smith]

Ok I think I have enough info to give this another attempt.

 

Thank you so much for all your help Jimmy, I really appreciate it.

 

p.s. If you drop this info on the StackOverflow I’ve linked at the bottom of the original article, I’ll hand you my 100 bounty points also J