WPF - MVVM - XAML 绑定问题

Question

I'm doing a simple WPF application which has a first ObservableList of ViewModels:

public OuterViewModel CurrentItem
{
    get;
    set;
}

public ObservableCollection<OuterViewModel> OuterItems
{
    get;
    set;
}

The OuterViewModel has these objects:

 public string Description
 {
      get;
      private set;
 }

 public ObservableCollection<InnerViewModel> Ruote
 {
    get;
    private set;
 }

The inner view model:

public string Name
{
get;
set;
}

public Numbers Row
{
    get;
    set;
}

The Numbers object has simply five numeric properties. About the XAML:

<Window.DataContext>
    <local:MainWindowViewModel />
</Window.DataContext>
<ListBox Grid.Column="0" ItemsSource="{Binding OuterItems}" SelectedItem="{Binding CurrentItem}">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <Label Content="{Binding Name}" />
                </StackPanel>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
<ListView Grid.Column="1" ItemsSource="{Binding CurrentItem.Ruote}">
        <ListView.View>
            <GridView>
                <GridViewColumn Header="Name" DisplayMemberBinding="{Binding ?}"/>
                <GridViewColumn Header="Primo" />
                <GridViewColumn Header="Secondo" />
                <GridViewColumn Header="Terzo" />
                <GridViewColumn Header="Quarto" />
                <GridViewColumn Header="Quinto" />
            </GridView>
        </ListView.View>
    </ListView>

The Listbox shows correctly, while the Intellisense says that I can select CurrentItem.Ruote for ListView.ItemSource. Now I want to fill the rows of ListView with Ruote items and here comes the troubles: I can't select the InnerViewModel properties to put in the cells. What am I doing wrong?

Answer 1

You need something to communicate that properties changed.

You can implement the INotifyPropertyChanged interface. For example:

public class ViewModel : INotifyPropertyChanged
{
    private OuterViewModel currentItem;
    public OuterViewModel CurrentItem
    {
        get { return currentItem; }
        set
        {
            currentItem = value;
            NotifyPropertyChanged(nameof(CurrentItem));
        }
    }

    private void NotifyPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

    public event PropertyChangedEventHandler PropertyChanged;
}