Question

I have an ObservableCollection of ChildViewModels with somewhat complex behaviour.

When I go to edit a row – the DataGrid goes into ‘edit-mode’ – this effectively disables UI-notifications outside the current cell until the row is committed – is this intended behaviour and more importantly can it be changed?

Example:

public class ViewModel
{
    public ViewModel()
    {
        Childs = new ObservableCollection<ChildViewModel> {new ChildViewModel()};
    }
    public ObservableCollection<ChildViewModel> Childs { get; private set; }
}
public class ChildViewModel : INotifyPropertyChanged
{
    private string _firstProperty;
    public string FirstProperty
    {
        get { return _firstProperty; }
        set
        {
            _firstProperty = value;
            _secondProperty = value;
            OnPropetyChanged("FirstProperty");
            OnPropetyChanged("SecondProperty");
        }
    }

    private string _secondProperty;
    public string SecondProperty
    {
        get { return _secondProperty; }
        set
        {
            _secondProperty = value;
            OnPropetyChanged("SecondProperty");
        }
    }

    private void OnPropetyChanged(string property)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(property));
    }
    public event PropertyChangedEventHandler PropertyChanged;
}

And in View:

<Window.Resources>
    <local:ViewModel x:Key="Data"/>
</Window.Resources>
<DataGrid DataContext="{Binding Source={StaticResource Data}}" ItemsSource="{Binding Childs}"/>

Notice how the second notification when editing first column is hidden until you leave the row.

EDIT: Implementing IEditableObject does nothing:

public class ChildViewModel : INotifyPropertyChanged,IEditableObject
{
    ...
    private ChildViewModel _localCopy;

    public void BeginEdit()
    {
        _localCopy = new ChildViewModel {FirstProperty = FirstProperty, SecondProperty = SecondProperty};
    }

    public void EndEdit()
    {
        _localCopy = null;
    }

    public void CancelEdit()
    {
        SecondProperty = _localCopy.SecondProperty;
        FirstProperty = _localCopy.FirstProperty;
    }
}

Answer 1

This behavior is implemented in DataGrid using BindingGroup. The DataGrid sets ItemsControl.ItemBindingGroup in order to apply a BindingGroup to every row. It initializes this in MeasureOverride, so you can override MeasureOverride and clear them out:

public class NoBindingGroupGrid
    : DataGrid
{
    protected override Size MeasureOverride(Size availableSize)
    {
        var desiredSize = base.MeasureOverride(availableSize);
        ClearBindingGroup();
        return desiredSize;
    }

    private void ClearBindingGroup()
    {
        // Clear ItemBindingGroup so it isn't applied to new rows
        ItemBindingGroup = null;
        // Clear BindingGroup on already created rows
        foreach (var item in Items)
        {
            var row = ItemContainerGenerator.ContainerFromItem(item) as FrameworkElement;
            row.BindingGroup = null;
        }
    }
}