Question

I have a ListView which I filled in from SQL Server view called view_ListaKlientow with this query:

    private void fillClientsList() {
        using (var context = new EntityBazaCRM()) {
            var listaKlientow = from d in context.view_ListaKlientow
                                select d;
            objectListViewListaKlientow.SetObjects(listaKlientow.ToList());
            objectListViewListaKlientow.AutoResizeColumns();
        } 
    }

Then after user double clicks one row in ListView, I read ID from the view_ListaKlientow and use fillClientGui to fill necessary fields in gui (for a test only one field is included).

    private void objectListViewListaKlientow_DoubleClick(object sender, EventArgs e) {
        foreach (view_ListaKlientow user in objectListViewListaKlientow.SelectedObjects) {
            int id = user.KlienciID;
            fillClientGui(id);
            TabPageActivate(tabControlMain, tabPageKlient);
        }
    }
    private void fillClientGui(int klientId) {
        using (var context = new EntityBazaCRM()) {
            IQueryable<Klienci> klient = context.Kliencis.Include("Podmioty").Where(d => d.KlienciID == klientId);
            foreach (var source in klient.ToList()) {
                textNIP.Text = source.Podmioty.PodmiotNIP;
            }
        }
    }

Now I’m wondering since I know exactly I’m querying for one ID i should be getting only particular client and not a list of clients so foreach from fillClientGui just to travers IQueryable<Klienci> seems like additional unnecessary code. Or this is how it should be done? I’m trying to learn Entity and some things aren’t just clear to me yet 🙂

Answer 1

If you’re sure that you’ve got only one instance to be returned form the database, you can use the extension function FirstOrDefault() in this case:

var source = context.Kliencis.Include("Podmioty").Where(d => d.KlienciID == klientId).FirstOrDefault();
textNIP.Text = source.Podmioty.PodmiotNIP;