Automapper mapping issue: flattening from DTO to ViewModel works - doesn't work the other way around

My DTOs (simplified for demonstration purposes):

Item (the DTO mapped to my ViewModel in question):

public class Item {
    public Item() { }
    public virtual Guid ID { get; set; }
    public virtual ItemType ItemType { get; set; }
    public virtual string Title { get; set; }
}

ItemType (referenced by my Item class):

public class ItemType {
    public ItemType() { }
    public virtual Guid ID { get; set; }
    public virtual IList<Item> Items { get; set; }
    public virtual string Name { get; set; }
}

My ViewModel (for editing my Item class data):

public class ItemEditViewModel {
    public ItemEditViewModel () { }
    public Guid ID { get; set; }
    public Guid ItemTypeID { get; set; }
    public string Title { get; set; }
    public SelectList ItemTy开发者_开发百科pes { get; set; }
    public IEnumerable<ItemType> ItemTypeEntities { get; set; }

    public BuildItemTypesSelectList(Guid? itemTypeID)
    {
        ItemTypes = new SelectList(ItemTypeEntities, "ID", "Name", itemTypeID);
    }
}

My AutoMapper mapping code:

Mapper.CreateMap<Item, ItemEditViewModel>()
    .ForMember(dest => dest.ItemTypes, opt => opt.Ignore());
Mapper.CreateMap<ItemEditViewModel, Item>();

Controller code (again, simplified for demonstration):

public ActionResult Create()
{
    var itemVM = new ItemEditViewModel();
    // Populates the ItemTypeEntities and ItemTypes properties in the ViewModel:
    PopulateEditViewModelWithItemTypes(itemVM, null);
    return View(itemVM);
}

[HttpPost]
public ActionResult Create(ItemEditViewModel itemVM)
{
    if (ModelState.IsValid) {
        Item newItem = new Item();
        AutoMapper.Mapper.Map(itemVM, newItem);
        newItem.ID = Guid.NewGuid();
        ...
        // Validation and saving code here...
        ...
        return RedirectToAction("Index");
    }

    PopulateEditViewModelWithItemTypes(itemVM, null);
    return View(itemVM);
}

Now, here's what's happening:

Within my HttpPost Create action result in my controller where I use Automapper to map my ItemEditViewModel to my Item DTO class, the ItemType ID value selected in the SelectList doesn't bind to the Item.ItemType.ID property. The Item.ItemType property is null.

I assume this is because, since I don't have an ItemTypeID Guid value in my Item DTO class, and I haven't created a new ItemType class for the property of the same name in my Item DTO, AutoMapper is unable to store the ItemType ID value.

I think it comes down to my Automapper mapping configuration.

I'm sure it's something simple that I'm overlooking.

Thanks in advance for any advice!

---

Pretty sure this is because automapper was designed as a Big Shape-> Smaller/Flat Shape mapping tool, not the other way around. This just isn't supported.

---

You should be able to say:

Mapper.CreateMap<ItemEditViewModel, Item>()
    .ForMember(dest => dest.ItemType, opt => opt.MapFrom(src =>
        {
            return new ItemType()
                {
                    ID = src.ItemTypeID
                }
        };