Question

I have a view for editing a specific project. Here is what I do for preparing a view model for this view:

1. Retrieve project info
2. Prepare a new view model object anp map my project into it.
3. Prepare a TechnologyString by calling a function to fill it.

4. Showing the view.

   public ActionResult Edit(string slug)
   {
       // 1
       Project project = m_ProjectBusiness.GetProject(slug);
   
       // 2
       ProjectEditViewModel viewModel = new ProjectEditViewModel
       {
           ProjectToEdit = Mapper.Map<Project, ProjectFullViewModel>(project)                 
       };
   
       // 3
       viewModel.ProjectToEdit.TechnologyString = m_ProjectBusiness.ListTechnologies(project);
   
       // 4
       return View(viewModel);
   }
   

As you can see for point 3, I fill in a string (TechnologyString) located in my view model, under my object ProjectToEdit. I would like to know if it is possible to do this operation directly (and automatically) when the mapping occurs?

Thanks.

---

EDIT

I found a solution based on mapping. Here it is:

        Mapper.CreateMap<Project, ProjectFullViewModel>()
             .ForMember(dest => dest.TechnologyString,
                        opt => opt.MapFrom(src => String.Join(" ", src.Technologies.Select(x => x.Name))));

So, I retrieve every technologies attached to my project and create a string with all items separated by a space.

Readers: Please note that Darin’s solution below works in case of Technologies are not part of my domain model. But in this case it is.

Answer 1

This is not something that should be handled at your mapping level. You could use a service layer in which you will define an aggregate root for the project and the technology:

public class ProjectAggregateRoot
{
    public Project Project { get; set; }
    public string TechnologyString { get; set; }
}

and then have a method in your service layer that will return this aggregate root:

public ProjectAggregateRoot GetProjectBySlug(string slug)
{
    var project = _repo.GetProject(slug);
    var technoString = _repo.ListTechnologies(project);
    return new ProjectAggregateRoot
    {
        Project = project,
        TechnologyString = technoString
    }
}

and then you could directly map between the aggregate root that will be returned by your service layer and the view model, like so:

public ActionResult Edit(string slug)
{
    var model = _service.GetProjectBySlug(slug);

    // now you have everything in the aggregate root to build your view model
    var viewModel = Mapper.Map<ProjectAggregateRoot, ProjectEditViewModel>(model);
    return View(viewModel);
}