Question

I am currently working with EnterpriseLibrary 5.0 and MVVM:

I have an ObservableCollection ListCategories<Category> property binded to an editable ComboBox (I can add/delete/edit categories):

I have the following code:

public ObservableCollection<Category> ListCategories
        {
            get
            {
                return listCategories;
            }

            set
            {
                listCategories = value;
            }
        }
    var categories = sdb.ExecuteSprocAccessor <Category> ("Get_Categories_List");

                 ListCategories = categories.ToObservableCollection <Category>();

My question:

After all changes made in the collection, how to update back the database?

Thanks

Answer 1

The proper way is to have a DB Access layer behind the Repository pattern of:

public interface IRepository<T>
{
   IEnumerable<T> GetAll();
   T GetById(int id);
   void Save(T saveThis);
   void Delete(T deleteThis);
}

then implement this with your domain type Category (I’m assuming that’s a domain type and not a type generated by an ORM.

public interface ICategoryRepository : IRepository<Category>
{
    // add any methods that are needed to act on this specific repo
}

then set the dependency in the ViewModel to this ICategoryRepository;

private readonly ICategoryRepository _categoryRepo;

public ViewModel(ICategoryRepository categoryRepo)
{
    _categoryRepo = categoryRepo;
}

Then act on this dependency from your ViewModel, your ViewModel SHOULD NOT be calling a database directly which is what you seem to be implying.

your code:

sdb.ExecuteSprocAccessor <Category> ("Get_Categories_List");

should reside in the GetAll() of the repository. Move it out of the ViewModel.

your setting of the observable collection should be done in the ctr:

ListCategories = categories.ToObservableCollection <Category>();

to this:

public ViewModel(ICategoryRepository categoryRepo)
{
    _categoryRepo = categoryRepo;
    var categories = _categoryRepo.GetAll();
    ListCategories = categories.ToObservableCollection <Category>();
}