/// <summary>
/// INotifyCollectionChanged.CollectionChanged handler for updating DataGrid.SelectedItems when the source list changes
/// </summary>
private static void UpdateDataGridsOnSourceCollectionChanged(object source, NotifyCollectionChangedEventArgs collectionChangedArgs)
{
DataGridsAndInitiatedSelectionChange sourceListInfo = ListViewMultipleSelection.selectedItemsSources[source.GetHashCode()];
// For each DataGrid that is bound to this list, is alive, and did not initate selection changes, update its selection
sourceListInfo.InitiatedSelectionChange = true;
IList sourceList = source as IList;
Debug.Assert(sourceList != null, "SelectedItemsSource must be of type IList");
ListView dataGrid = null;
foreach (WeakReference dataGridReference in sourceListInfo.BoundDataGridReferences)
{
if (dataGridReference.IsAlive && !ListViewMultipleSelection.GetInitiatedSelectionChange(dataGridReference.Target as ListView))
{
dataGrid = dataGridReference.Target as ListView;
UpdateDataGrid(dataGrid, sourceList, collectionChangedArgs);
}
}
sourceListInfo.InitiatedSelectionChange = false;
}
/// <summary>
/// Updates the items source registry when the SelectedItemsSource for a DataGrid changes
/// </summary>
private static void SelectedItemsSourceChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args)
{
ListView dataGrid = sender as ListView;
IList selectedItemsSource = null;
// Check if the app is setting the source to a new or different list, or if it is removing the binding
if (args.NewValue != null)
{
selectedItemsSource = args.NewValue as IList;
if (selectedItemsSource == null)
{
throw new ArgumentException("The value for SelectedItemsSource must implement IList.");
}
INotifyCollectionChanged collection = args.NewValue as INotifyCollectionChanged;
if (collection == null)
{
throw new ArgumentException("The value for SelectedItemsSource must implement INotifyCollectionChanged.");
}
// Don't add the event handler if the DataGrid is not setting its SelectedItemsSource for the first time
if (args.OldValue == null)
{
// Sign up for changes to the DataGrid's selected items to enable a two-way binding effect
dataGrid.SelectionChanged += UpdateSourceListOnDataGridSelectionChanged;
}
// Track this DataGrid instance for the specified source list
DataGridsAndInitiatedSelectionChange sourceListInfo = null;
if (ListViewMultipleSelection.selectedItemsSources.TryGetValue(selectedItemsSource.GetHashCode(), out sourceListInfo))
{
sourceListInfo.BoundDataGridReferences.Add(new WeakReference(dataGrid));
}
else
{
// This is a new source collection
sourceListInfo = new DataGridsAndInitiatedSelectionChange()
{
InitiatedSelectionChange = false
};
sourceListInfo.BoundDataGridReferences.Add(new WeakReference(dataGrid));
ListViewMultipleSelection.selectedItemsSources.Add(selectedItemsSource.GetHashCode(), sourceListInfo);
// Sign up for changes to the source only on the first time the source is added
collection.CollectionChanged += UpdateDataGridsOnSourceCollectionChanged;
}
// Now force the DataGrid to update its SelectedItems to match the current
// contents of the source list
sourceListInfo.InitiatedSelectionChange = true;
UpdateDataGrid(dataGrid, selectedItemsSource, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
sourceListInfo.InitiatedSelectionChange = false;
}
else
{
// This DataGrid is removing its SelectedItems binding to any list
dataGrid.SelectionChanged -= UpdateSourceListOnDataGridSelectionChanged;
dataGrid.SelectedItems.Clear();
}
if (args.OldValue != null)
{
// Clean up the items source that was the old value
// Remove the DataGrid from the source list's registry and remove the source list
// if there are no more DataGrids bound to it.
DataGridsAndInitiatedSelectionChange sourceListInfo = ListViewMultipleSelection.selectedItemsSources[args.OldValue.GetHashCode()];
WeakReference dataGridReferenceNeedingRemoval = null;
foreach (WeakReference dataGridReference in sourceListInfo.BoundDataGridReferences)
{
if (dataGridReference.IsAlive && (dataGridReference.Target == dataGrid))
{
dataGridReferenceNeedingRemoval = dataGridReference;
break;
}
}
sourceListInfo.BoundDataGridReferences.Remove(dataGridReferenceNeedingRemoval);
if (sourceListInfo.BoundDataGridReferences.Count == 0)
{
ListViewMultipleSelection.selectedItemsSources.Remove(args.OldValue.GetHashCode());
// Detach the event handlers and clear DataGrid.SelectedItems since the source is now null
INotifyCollectionChanged collection = args.OldValue as INotifyCollectionChanged;
if (collection != null)
{
collection.CollectionChanged -= UpdateDataGridsOnSourceCollectionChanged;
}
}
}
}