Question

I have an unusual requirement. I have a WPF Datagrid with 5 rows. If I changed any cell under ColumnB, then all rows under ColumnB should be notified.

Right now after updating one cell under ColumnB, only that cell gets updated, and if I doubleclick on any other cell under ColumnB and get into the Edit Mode, ONLY THEN the new value is displayed.

How do I force a RaisePropertyChanged on all rows, if one row has been updated?

Answer 1

Usually I would do this in the codebehind containing the DataGrid’s ItemsSource

Here’s a rough example:

MyObservableCollection.CollectionChanged += MyObservableCollection_CollectionChanged;

...

void MyObservableCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
    // Attach PropertyChange event to item
    if (e.NewItems != null)
        foreach (SomeDataItem item in e.NewItems)
            item.PropertyChanged += SomeDataItem_PropertyChanged;

    if (e.OldItems != null)
        foreach (SomeDataItem item in e.OldItems)
            item.PropertyChanged -= SomeDataItem_PropertyChanged;
}

private bool shouldUpdate = true;

void SomeDataItem_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
    // If PropertyChanged raised on ColumnB, and shouldUpdate flag is true
    if (e.PropertyName == "ColumnB" && shouldUpdate)
    {
        // Disable updating all collections to prevent infinite looping
        shouldUpdate = false;

        foreach (SomeDataItem item in e.NewItems)
        {
            // If this isn't the current item, raise a PropertyChanged event on ColumnB
            if (item != sender)
                item.RaisePropertyChanged(e.PropertyName);
        }

        // Reenable updating all collections
        shouldUpdate = true;
    }
}