Question

I have a MVVM setup that creates a View on my MainWindow. I am not sure how to know when a user Clicks on a specific Notification Item inside the View. Where would I add the event, or a command to know when that happens?

here are is my MVVM code :

MainWindow

cs:

NotificationViewModel notificationViewModel = new NotificationViewModel();
notificationViewModel.AddNoticiation(new NotificationModel() { Message = "Error", Name = "Station 21" });
NotificationView.DataContext = notificationViewModel;

xaml:

<notification:NotificationView x:Name="NotificationView" />

NotificationModel

public class NotificationModel : INotifyPropertyChanged
{

    private string _Message;
    public string Message
    {
        get { return _Message; }
        set
        {
            if (_Message != value)
            {
                _Message = value;
                RaisePropertyChanged("Message");
            }
        }
    }

    private string _Name;
    public string Name
    {
        get { return _Name; }
        set
        {
            if (_Name != value)
            {
                _Name = value;
                RaisePropertyChanged("Name");
            }
        }
    }

    public string TimeStamp
    {
        get { return DateTime.Now.ToString("h:mm:ss"); }
    }

    #region PropertChanged Block
    public event PropertyChangedEventHandler PropertyChanged;

    private void RaisePropertyChanged(string property)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(property));
        }
    }
    #endregion
}

NotificationViewModel

public class NotificationViewModel 
{
    private ObservableCollection<NotificationModel> _Notifications = new ObservableCollection<NotificationModel>();
    public ObservableCollection<NotificationModel> Notifications 
    { 
        get { return _Notifications; } 
        set { _Notifications = value; } 
    }

    public void AddNoticiation(NotificationModel notification)
    {
        this.Notifications.Insert(0, notification);
    }
}

NotificationView

<Grid>
    <StackPanel HorizontalAlignment="Left" >
        <ItemsControl ItemsSource="{Binding Path=Notifications}"
                      Padding="5,5,5,5">
            <ItemsControl.ItemTemplate>
                <DataTemplate>
                    <Border Background="SlateGray"
                            CornerRadius="4">
                        <Grid>
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="100" />
                                <ColumnDefinition Width="100" />
                                <ColumnDefinition Width="100" />
                            </Grid.ColumnDefinitions>
                            <TextBlock Grid.Column="0" 
                                       Text="{Binding Path=TimeStamp}" />
                            <TextBlock Grid.Column="1" 
                                       Text="{Binding Path=Name}" />
                            <TextBlock Grid.Column="2" 
                                       Text="{Binding Path=Message}" />
                        </Grid>
                    </Border>
                </DataTemplate>
            </ItemsControl.ItemTemplate>
        </ItemsControl>
    </StackPanel>
</Grid>

Answer 1

There’s no real selection mechanism built into an ItemsControl. It would probably solve your problem to switch out your ItemsControl for a ListBox.

If you do that, you can bind to SelectedItem, then handle any changes made to SelectedItem using the PropertyChanged event.

Example:

In your view model’s constructor:

PropertyChanged += NotificationViewModel_PropertyChanged;

Add a property to your view model to allow the binding:

private string _selectedNotification;
public string SelectedNotification
{
    get { return _selectedNotification; }
    set
    {
        if (_selectedNotification != value)
        {
            _selectedNotification = value;
            RaisePropertyChanged("SelectedNotification");
        }
    }
}

Finally, add the event handler to your view model:

NotificationViewModel_PropertyChanged(object sender, PropertyChangedEventArgs e))
{
    if (e.PropertyName = "SelectedNotification") DoStuff();
}

You may find that you don’t even need to hook into PropertyChanged if you just want to update another control in your view based on the selected item in your list box. You can just bind directly to the property within xaml.