Repository pattern and mapping between domain models and Entity Framework

Question

My repositories deal with and provide persistence for a rich domain model. I do not want to expose the anemic, Entity Framework data entity to my business layers, so I need

Answer 1

I like using custom-built Extension methods to do the mapping between Entity and Domain objects.

• You can easily call extension methods for other entities when they are within a containing entity.
• You can easily deal with collections by creating IEnumerable<> extensions.

A simple example:

public static class LevelTypeItemMapping
{
    public static LevelTypeModel ToModel(this LevelTypeItem entity)
    {
        if (entity == null) return new LevelTypeModel();

        return new LevelTypeModel
        { 
            Id = entity.Id;
            IsDataCaptureRequired = entity.IsDataCaptureRequired;
            IsSetupRequired = entity.IsSetupRequired;
            IsApprover = entity.IsApprover;
            Name = entity.Name;
        }
    }
    public static IEnumerable ToModel(this IEnumerable entities)
    {
        if (entities== null) return new List();

        return (from e in entities
                select e.ToModel());
    }

}

...and you use them like this.....

 using (IUnitOfWork uow = new NHUnitOfWork())
        {
        IReadOnlyRepository repository = new NHRepository(uow);
        record = repository.Get(id);

        return record.ToModel();

        records = repository.GetAll(); // Return a collection from the DB
        return records.ToModel(); // Convert a collection of entities to a collection of models
        }

Not perfect, but very easy to follow and very easy to reuse.