Bubbling up WPF Datagrid Item events - wpf

Question

I've a datagrid with an ItemsSource of ObservableCollection (OC) of objects. When an item's property changes, I want to work on the OC itself .
E.g. I've an item which is approved for uploading to our database. However, I need to loop through the OC to check if other items exist in the collection which already fit the set criteria, so that I may actually not have to upload the selected item.
On the datagrid, when I tick the checkbox of an item, it will change the boolean value (e.g. "IsToUpload") of the item, and an event should trigger on the property change.
I'm assuming I will then need to 'bubble up' my event notifications to the datagrid/mainwindow class, where I can then work on the OC. How may I do this, and if this is not the correct way, what should I be doing?
I've followed Aran Mulholland's class structure to colour my rows dynamically: Coloring WPF DataGridRows one by one
So my class structure is roughly as follows:
MainWindow -> DataGrid
-> ObservableCollection<ItemObjectViewModel:NotificationObject>
ItemObject : INotifyPropertyChanged //this class is where I
//store my item variables. It is referenced through properties
//in the ItemObjectViewModel.

Answer 1

Event bubling \ routing etc works for dependency objects in a visual \ logical tree. Your NotificationObject is not a dependency object and neither is it hosted in the visual tree.... What we have in visual tree are the checkboxes (that are bound to your NotificationObject).
Non MVVM
In you DataGrid you would have to Tag your Checkboxes with some identification and then use ButtonBase.Click="" event at datagrid level which will be handled for any click event bubbled for any button based eleemnt (such as buttons, menuitems, togglebuttons, checkboxes, radioboxes, comboboxes) that gets clicked in the entire visual tree of the datagrid.
In the handler verify if the e.OriginalSource is a checkbox and that its Tag is same as the identification value we have set in the XAML of the datagrid. That way we know that the CheckBox is clicked.
E.g.
<DataGrid AutogenerateColumns="False"
ItemsSource="{Binding NotificationObjectCollection}"
ButtonBase.Clicked="OnNotificationCheckBoxClicked">
<DataGrid.Columns>
<DataGridCheckBoxColumn Binding="{Binding IsClicked}"
Header="Click?">
<DataGridCheckBoxColumn.ElementStyle>
<Style TargetType="{x:Type CheckBox}">
<Setter Property="Tag" Value="IsClickCheckBox" />
</Style>
</DataGridCheckBoxColumn.ElementStyle>
</DataGridCheckBoxColumn>
</DataGrid.Columns>
</DataGrid>
private void OnNotificationCheckBoxClicked
(object sender, RoutedEventArgs e)
{
if (e.OriginalSource is CheckBox)
{
if (((CheckBox)e.OriginalSource).Tag == "IsClickCheckBox")
{
var notificationObject
= ((CheckBox)e.OriginalSource).DataContext
as NotificationObject;
if (notificationObject.IsClicked) { }
else { }
}
}
}
MVVM
The only way MVVM can notify the ancestor object in the visual is by using Command execution as the underlying NotificationObject gets checked (setter is called) we execute the command supplied to the NotificationObject.
Use the weak reference based RelayCommand or DelegateCommand (as available on the internet) for this purpose.
Add a new NotificationObject constructor
private ICommand _isClickedCommand;
public NotificationObject(ICommand isClickedCommand)
{
_isClickedCommand = isClickedCommand;
}
private bool _isClicked;
public bool IsClicked
{
get
{
return _isClicked;
}
set
{
if (_isClicked != value)
{
_isClicked = value;
OnPropertyChanged("IsClicked");
isClickedCommand.Execute(this);
}
}
}
Using the notification object
public class ItemObjectViewModel
{
private DelegateCommand<NotificationObject>
_notificationObjectClickedCommand
= new DelegateCommand<NotificationObject>(
OnNotificationObjectCommandExecute);
....
private void PopulateCollection()
{
NotificationObjectCollection
= new ObservableCollection<NotificationObject>();
NotificationObjectCollection.Add(
new NotificationObject(_notificationObjectClickedCommand));
}
private void OnNotificationObjectCommandExecute(
NotificationObject notificationObject)
{
if (notificationObject.IsClicked) { }
else { }
}
}
You can also achieve the ICommand based behavior in non MVVM scenario by using 'RoutedCommand'
Let me know if this helps...