Question

I would like to heard what is suitabale solution for this situation.

I use in WPF app Caliburn.Micro framework. I need have acess to SQL Compact DB.
On DB access I use LINQ TO SQL.

For example In view I have comboBox control or listBox control.
I need load items of these controls from DB.

So I create simple class on access to the DB.

[Export(typeof(IDbManager))]
public partial class DbManager : IDbManager
{

    public IList<Spirit_Users> LoadSpiritUsers()
    {
        var result = from u in _dc.Spirit_Users orderby u.Nick select u;
        return result.ToList();
    }
}

I inject this class with MEF to view model class.
On use method from class on DB access in my view model class on load items to comboBox.

[Export(typeof(ILogOnViewModel))]
public class LogOnViewModel : Screen, ILogOnViewModel,
    IPartImportsSatisfiedNotification
{
    [Import]
    internal IDbManager DbManager { get; set; }

    //this property is bind on listbox or comboBox
    public BindableCollection<Spirit_Users> SpiritUsers
    {
        get { return _spiritUsers; }
        set
        {
            _spiritUsers = value;
            NotifyOfPropertyChange(() => SpiritUsers);
        }
    }


    private void ConfigureSpiritUsers()
    {
        //load items from comboBox or listBox
        var users = SettingsDbManager.LoadSpiritUsers();

        //add to the collection which is binded on control in view
        if (users.Count > 0)
        {
            foreach (var user in users)
            {
                SpiritUsers.Add(user);
            }
        }
    }


    protected override void OnActivate()
    {
        ConfigureSpiritUsers();
        base.OnActivate();
    }
}

I don’t know if my solution is correct and the most suitable in scenarion WPF app with MVVVM.

Also I need create CRUD operation from view model class to the DB. For example save some object/data to the database.

Thank for advice.

Answer 1

This looks fine, in ConfigureSpiritUsers you reference SettingsDbManager, where is this defined? Should this be DbManager instead?

Really, DbManager is a SpiritUserRepository, and could include your other CRUD operations as methods on the interface and concrete implementation. As long as your view models are always working against abstractions, then that is fine.

Also, you could populate the SpiritUsers collection in one line with this.SpiritUsers = new BindableCollection(users). I would also make the type of SpiritUsers an IObservableCollection<Spirit_User>, or better still an abstraction of Spirit_User (i.e. ISpiritUser).