Wpf databinding collection update after insert using Entity Framework

jose silveira

4y1.4kWPF

Hi everyone, i'n learning c#, currently using wpf and databinding, i've created the models and view model:

 public class MedidasViewModel : ObservableObject
    {
        public ObservableCollection _medidas;

        public ObservableCollection Medidas
        {
            get { return _medidas; }
            set { _medidas = value; }
        }

        public  MedidasViewModel()
        {
            _medidas = new ObservableCollection();

            using (AppDbContext context = new AppDbContext())
            {
                List lista = context.Medida.ToList();


                foreach (var item in lista)
                {
                    _medidas.Add(item);

                }
            }
        }
        
    }

When i load the window, it get all the data, but when i add a new medida into the database, my combobox doesn't update.

public partial class NovaMedida : ObservableObject
    {
        [ObservableProperty]
        [NotifyPropertyChangedFor(nameof(DescricaoNovaMedida))]
        string descricaoN;

        [ObservableProperty]
        [NotifyPropertyChangedFor(nameof(SiglaNovaMedida))]
        string siglaN;

        [ObservableProperty]
        [NotifyPropertyChangedFor(nameof(ConvervorNovaMedida))]
        decimal conversorN;
        public string DescricaoNovaMedida => descricaoN;
        public string SiglaNovaMedida => siglaN;
        public double ConvervorNovaMedida => Convert.ToDouble(conversorN);
        [RelayCommand]
        void SalvarNovaMedida()
        {
            Medida medida = new Medida();
            medida.Descricao = DescricaoNovaMedida;
            medida.Sigla = SiglaNovaMedida;
            medida.Conversor = Convert.ToDecimal(ConvervorNovaMedida);
            using (var context = new AppDbContext())
            {
                context.Medida.Add(medida);
                context.SaveChanges();
               
            }
            

        }
       
    }

I've googled for days i coun't find a solution

2 Replies

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Aymen Amri4y ago
Another two points that I found when reviwing your post :
you need to call Medidas.Add(item); instead of _medidas.Add(item); to raise the notifypropertychanged.
Review your binding of the Item source MedidasView.Medidas you need to bind on the property Medidas of your MedidasViewModel (ensure that it's your view's dataContext).
Aymen Amri4y ago
Try to implement INotifyPropertyChanged directly from your viewModel
public class MedidasViewModel : ObservableObject,INotifyPropertyChanged
Then you need to implement the interface's method :
public event PropertyChangedEventHandler PropertyChanged;
public void NotifyPropertyChanged([CallerMemberName] string propertyName = "")
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public ObservableCollection Medidas
       {
           get { return _medidas; }
           set {
_medidas = value;
NotifyPropertyChanged("Medidas");
}
       }