WPF ComboBox Databinding not updating

Question

As seen in the picture i have a ComboBox which is showing me all the Events that i have in my Database. This could be a birthday party for example. The Listview is showing me the participants. This is all working perfect. But, when i add a new Event in the running application, using the textboxes nd the button "Toevoegen" Which translates to "Add" My Combobox is not showing the new event. When i restart the program it does show it.

I figured out that it has something to do with the property changed. But how do i use this when i add my items to an instance of eventmanager.events.Add(item)?

Xaml

Eventmanager Class

public class EventManager : INotifyPropertyChanged
{
    public List events { get; set; }
    public List peoples { get; set; }

    //this is the current event that correspond to the selected event in your combobox
    private Event _currentEvent;
    public Event currentEvent
    {
        get
        {
            return _currentEvent;
        }
        set
        {
            if (_currentEvent != value)
            {
                _currentEvent = value;
                //when you change the selected event, you have to update the list of participants
                OnPropertyChanged("participants");
            }
        }
    }

    public List participants
    {
        get
        {
            //Here is the code to retrieve the people that registered to the selected event
            return peoples.Where(p => p.registeredEvents.Contains(currentEvent)).ToList();
        }
    }

    public EventManager()
    {
        events = new List();
        peoples = new List();
    }

    //The following lines are specific to WPF and DataBinding
    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }


}

People Class

public class People : INotifyPropertyChanged
{
    public string firstName { get; set; }
    public string lastName { get; set; }

    public List registeredEvents { get; set; }

    public People()
    {
        registeredEvents = new List();
    }

    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }
}

public class Event : INotifyPropertyChanged
{
    public string name { get; set; }
    public string omschrijving { get; set; }
    public string opmerking { get; set; }
    public DateTime Datum { get; set; }



    //The following lines are specific to WPF and DataBinding
    public event PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string name)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
        {
            handler(this, new PropertyChangedEventArgs(name));
        }
    }

}

This is how i add my events and participants:

    EventManager eventManager = new EventManager();
    DBConnect connect = new DBConnect();
    public Event Selected;

private void btnAdd_Click(object sender, RoutedEventArgs e)
    {

        connect.EvToevoegen(tbNaamEv.Text, TbOmschrijvingEV.Text, tbOpmerkingEv.Text, Convert.ToDateTime(DPevenement.SelectedDate));

        Selected = new Event()
        {
            name = tbNaamEv.Text
        };

        eventManager.events.Add(Selected);

    }
}

The new Event won't show in my ComboBox?

etberg · Accepted Answer

Lists don't respond to the PropertyChanged events like you expect because the List itself likely never changed. Its contents did.

For ItemsSource to respond to a collection changing, that collection must implement the INotifyCollectionChanged interface. C# provides us with a collection that already implements that interface, thankfully.

If you use ObservableCollection you can get this functionality immediately.

Try replacing:

public List events { get; set; }

With:

public ObservableCollection events { get; set; }

If you are unable to change the type of this collection for whatever reason, you are going to need to wrap the list somehow.

The most simple way to do this is by using the copy constructor exposed by observable collection:

new ObservableCollection(IEnumerable)

WPF ComboBox Databinding not updating

Answers (2)

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