Question

I’m wondering about a “best practice” using NHibernate, AutoMapper and ASP.NET MVC. Currently, i’m using :

class Entity
{
    public int Id { get; set; }
    public string Label { get; set; }
}

class Model
{
    public int Id { get; set; }
    public string Label { get; set; }
}

Entity and model are mapped like this :

Mapper.CreateMap<Entity,Model>();
Mapper.CreateMap<Model,Entity>()
    .ConstructUsing( m => m.Id == 0 ? new Entity() : Repository.Get( m.Id ) );

And in the controller :

public ActionResult Update( Model mdl )
{
    // IMappingEngine is injected into the controller
    var entity = this.mappingEngine.Map<Model,Entity>( mdl );

    Repository.Save( entity );

    return View(mdl);
} 

Is this correct, or can it be improved ?

Answer 1

that’s how I was doing in a project:

public interface IBuilder<TEntity, TInput>
{
    TInput BuildInput(TEntity entity);
    TEntity BuildEntity(TInput input);
    TInput RebuildInput(TInput input);
}

implement this interface for each entity or/and for some group of entities you could do a generic one and use it in each controller; use IoC;

you put your mapping code in the first 2 methods (doesn’t matter the mapping technology, you could even do it by hand)
and the RebuildInput is for when you get the ModelState.IsValid == false, just call BuildEntity and BuildInput again.

and the usage in the controller:

        public ActionResult Create()
        {
            return View(builder.BuildInput(new TEntity()));
        }

        [HttpPost]
        public ActionResult Create(TInput o)
        {
            if (!ModelState.IsValid)
                return View(builder.RebuildInput(o));
            repo.Insert(builder.BuilEntity(o));
            return RedirectToAction("index");
        }

I actually do sometimes generic controller that is used for more entities
like here: asp.net mvc generic controller

EDIT:
you can see this technique in an asp.net mvc sample application here:
http://prodinner.codeplex.com