Databinding a ObservableCollection in MVVM

Question

I have a ListView with a Datatemplate that holds a list of Movies. It is databinded to a ObservableColection but whenever I edit the Movie.Name it does not update the ListView even though "Name" is called in my PropertyChangedEventHandler is called with "Name".

I add 2 "Movie"s to my collection in my initializer and these are shown correct (Klovn the Movie, Taken)

So when I click Edit it should change the text of the selected movie and change the Name of it to "Test" and is is changed but the change is not shown in the ListView but if I output Collection with a foreach then Name is Test.

View.xaml

<Window x:Class="MovieDB3.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <DockPanel>
        <Menu DockPanel.Dock="Top">
            <MenuItem Header="File">
                <MenuItem Header="Edit" Click="MenuEditClick"/>
            </MenuItem>
        </Menu>
        <Grid DockPanel.Dock="Top">
            <Grid.ColumnDefinitions>
                <ColumnDefinition/>
                <ColumnDefinition/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition/>
            </Grid.RowDefinitions>
            <ListView VerticalAlignment="Stretch" Name="ListViewMovies" ItemsSource="{Binding Path=Collection}" IsSynchronizedWithCurrentItem="True" >
                <ListView.ItemTemplate>
                    <DataTemplate>
                        <WrapPanel>
                            <TextBlock Text="{Binding Path=Name}"/>
                        </WrapPanel>
                    </DataTemplate>
                </ListView.ItemTemplate>
            </ListView>
        </Grid>
    </DockPanel>
</Window>

View.cs

using System;
using System.Windows;
using MovieDB3.Models;
using MovieDB3.ViewModels;

namespace MovieDB3
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private MainViewModel MVM;
        public MainWindow()
        {
            InitializeComponent();
            MVM = new MainViewModel();
            DataContext = MVM;
        }

        private void MenuEditClick(object sender, RoutedEventArgs e)
        {
            MVM.setMovieName((Movie)ListViewMovies.SelectedItem, "test");
        }
    }
}

The ViewModel

using System;
using System.ComponentModel;
using MovieDB3.Models;
using System.Collections.ObjectModel;

namespace MovieDB3.ViewModels
{
    class MainViewModel : INotifyPropertyChanged
    {
        public ObservableCollection<Movie> Collection {get; set;}

        public MainViewModel()
        {
            Collection = new ObservableCollection<Movie>();

            //Test kode
            Movie movie = new Movie();
            movie.Name = "Klovn The Movie";
            Collection.Add(movie);
            movie = new Movie();
            movie.Name = "Taken";
            Collection.Add(movie);
        }

        public void setMovieName(Movie movie, string newName)
        {
            //movie.Name = newName;
            Console.WriteLine("CurrentName: " + movie.Name);
            int i = Collection.IndexOf(movie);
            Collection[i].Name = newName;
            Console.WriteLine("NewName: " + movie.Name);
            NotifyPropertyChanged("Name");
        }

        public void setMovieName(string currentName, string newName)
        {
            foreach (Movie movie in Collection)
            {
                if (movie.Name.Equals(currentName))
                {
                    movie.Name = newName;
                    NotifyPropertyChanged("Name");
                    return;
                }
            }
        }

        //public string MovieName
        //{
        //    set 
        //    {

        //        NotifyPropertyChanged("MovieName");
        //    }
        //}

        public event PropertyChangedEventHandler PropertyChanged;

        private void NotifyPropertyChanged(String info)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(info));
            }
        }
    }
}

Movie.cs

using System;

namespace MovieDB3.Models
{
    class Movie
    {
        public string Name { get; set; }
        public int Id { get; set; }
        public double Rating { get; set; }
        public DateTime Release { get; set; }
        public TimeSpan Runtime { get; set; }
        public String Trailer { get; set; }
    }
}

Answer 1

INotifyPropertyChanged needs to be Implemented in your Movie class, also avoid raising the event manually. (Right now you are telling the View that the ViewModel's property "Name" changed, which does not exist)

---

What your class might look like:

public class Movie : INotifyPropertyChanged
{
    private string _name = String.Empty;
    public string Name
    {
        get { return _name; }
        set
        {
            if (_name != value)
            {
                _name = value;
                NotifyPropertyChanged("Name");
            }
        }
    }

    //...All the other properties (the same way)...

    public event PropertyChangedEventHandler PropertyChanged;

    public void NotifyPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }
}

What your changing method is reduced to:

    public void setMovieName(Movie movie, string newName)
    {
        Console.WriteLine("CurrentName: " + movie.Name);
        movie.Name = newName; //The notification is now raised automatically in the setter of the property in the movie class
        Console.WriteLine("NewName: " + movie.Name);
    }

Answer 2

I think the Movie itself needs to implement INotifyPropertyChanged. You are notifying via the wrong object (the viewmodel).

Answer 3

You need to implement INotifyPropertyChanged on your Movie class as well.

The notification that you are sending in the setMovieName method does not really mean anything - it's just a "property" name. It could just as well be "Foo," and your event handler will say "Foo".

What you need, instead, is for the Movie object itself to be updated.

Probably the best implementation will be for you to create an abstract class that notifies INotifyPropertyChanged, and then derive your ViewModel and your Movie classes from it, because both should implement it.

You will be binding properties from the ViewModel, and you will also be binding observable objects (i.e. Movie) inside that ViewModel.

Answer 4

Currently, you're having your MainViewModel raise the NotifyPropertyChanged event for Name changing. Instead, your Movie instances should be raising those events, since your Movie objects are what have that property bound.