更新ItemsControl中的绑定属性

Question

Quick description of my setup:

Disclaimer: The code is only to show what I want to do. The command binding for instance is done with event triggers etc. I'm pretty sure this wouldn't even build, but I didn't want to waste space.

My View:

<ItemsControl ItemsSource="{Binding Items}">
   <ItemsControl.ItemTemplate>
       <DataTemplate>
           <StackPanel>
               <TextBlock Text="{Binding IsFavorite, Converter={StaticResource FavoriteConverter}" Tap="{Binding FavoriteCommand, CommandParameter={Binding}}"/>
               <TextBlock Text="{Binding Title}"/>
            </StackPanel>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

My ViewModel:

public class ViewModel : ViewModelBase
{
    public IList<Item> Items { get; set; }
    public RelayCommand<Item> Favorite
    {
       get
       {
           return new RelayCommand<Item>(item =>
                {
                    item.IsFavorite = !item.IsFavorite;
                    RaisePropertyChanged(string.Empty);
                };
        }
     }
}

My Model:

public class Item
{
    public string Title { get; set; }
    public bool IsFavorite { get; set; }
}

* My Question: *

How can I get the IsFavorite-Property to update without implementing INotifyPropertyChanged? It's a model class, and I wouldn't like creating a ViewModel for the sole purpose of updating one property. I thought that calling PropertyChanged with an empty string would update everything, but alas it didn't.

* My Solution: *

public class ItemViewModel : ViewModelBase
{
    public Item Model { get; private set; }
    public bool IsFavorite
    {
        get { return Model.IsFavorite; }
        set
        {
            Model.IsFavorite = value;
            RaisePropertyChanged("IsFavorite");
        }
    }
}

Answer 1

If you are binding to the value and expect it to be changing at runtime, then you should really implement INotifyPropertyChanged since WPF's binding system uses that interface to know when it needs to update.

But with that said, you might be able to get away with raising a PropertyChange notification for the entire Items collection, although I'm not entirely sure that would work because the actual collection itself hasn't changed, only a property of one of the items inside the collection. And WPF usually knows not to bother re-evaluating a property if it doesn't actually change.

RaisePropertyChanged("Items");

If it doesn't work, you could probably remove the item and re-add it to trigger a CollectionChange notification, however that also might not work and may cause other problems depending on your application design.

// I may have the exact syntax wrong here
var index = Items.IndexOf(item);
var tmp = Items[index];
Items.Remove(tmp);
Items.Add(tmp, index);

But it would really just be best to implement INotifyPropertyChanged on your Item class.

Answer 2

Try to use: RaisePropertyChanged("Items"); and make Items collection ObservableCollection.

Implementing INotifyPropertyChanged is better.