GridvView.SelectedCells.Add() does not update view - wpf

Question

GridViews Selected cells is a IList, so it does not update the view, when i add selections from my ViewModel.
Is there a way to force updating the view for selected Cells. The way i currently uddate views is by having a Attached behavior, which updates the list on ViewModel, but also the GridView, but the GridView does not update its visuals.
here is my attached behavior:
public static List<GridCell> GetSelectedCells(DependencyObject obj)
{
return (List<GridCell>)obj.GetValue(SelectedCellsProperty);
}
public static void SetSelectedCells(DependencyObject obj, List<GridCell> value)
{
obj.SetValue(SelectedCellsProperty, value);
}
public static readonly DependencyProperty SelectedCellsProperty =
DependencyProperty.RegisterAttached("SelectedCells", typeof(List<GridCell>), typeof(DataGridHelper), new UIPropertyMetadata(null, OnSelectedCellsChanged));
static SelectedCellsChangedEventHandler GetSelectionChangedHandler(DependencyObject obj)
{
return (SelectedCellsChangedEventHandler)obj.GetValue(SelectionChangedHandlerProperty);
}
static void SetSelectionChangedHandler(DependencyObject obj, SelectedCellsChangedEventHandler value)
{
obj.SetValue(SelectionChangedHandlerProperty, value);
}
static readonly DependencyProperty SelectionChangedHandlerProperty =
DependencyProperty.RegisterAttached(nameof(SelectedCellsChangedEventHandler), typeof(SelectedCellsChangedEventHandler), typeof(DataGridHelper), new UIPropertyMetadata(null));
private static bool NewResouce = false;
static void OnSelectedCellsChanged(DependencyObject d, DependencyPropertyChangedEventArgs args)
{
if (d is DataGrid)
{
NewResouce = true;
DataGrid datagrid = d as DataGrid;
if (GetSelectionChangedHandler(d) == null)
{
SelectedCellsChangedEventHandler selectionchanged = (sender, e) =>
{
if (!NewResouce)
{
List<GridCell> cells = new List<GridCell>();
foreach (var selectedell in datagrid.SelectedCells)
{
string header = selectedell.Column.Header.ToString();
GridCell cell = new GridCell
{
RowIndex = datagrid.Items.IndexOf(selectedell.Item),
ColumnIndex = selectedell.Column.DisplayIndex,
Parent = selectedell.Item as ExpandoObject,
ColumnHeader = header,
Value = (selectedell.Item as IDictionary<string, object>)[header]
};
cells.Add(cell);
}
SetSelectedCells(d, cells);
}
};
SetSelectionChangedHandler(d, selectionchanged);
datagrid.SelectedCellsChanged += GetSelectionChangedHandler(d);
}
foreach (var selected in GetSelectedCells(d) as List<GridCell>)
{
DataGridCellInfo cell = new DataGridCellInfo(selected.Parent, datagrid.Columns[selected.ColumnIndex]);
if (!datagrid.SelectedCells.Contains(cell))
{
datagrid.SelectedCells.Add(cell);
}
}
NewResouce = false;
}
}
}
The reason why i have the NewResource boolean, is that the event selection changed does actually fire when I add newly selected items. Its just the view that does not update its selections.
The SelectedCells is added after the view is loaded, due to its located inside a tab, and it looks like the data on gridview is empty before view is loaded, so I cannot set selected before the view is loaded.

Answer 1

Answer is simple. Please use an ObservableCollection instead of the list.
The observable collection is a dependency object and it will raise a propertyChanged event to the view to notify it regarding the property change and the view will be updated.

Answer 2

I ended up finden some properties that does implement INotifyPropertyChanged, on DataGridCells heres the solution:
static void OnSelectedCellsChanged(DependencyObject d, DependencyPropertyChangedEventArgs args)
{
if (d is DataGrid)
{
DataGrid datagrid = d as DataGrid;
if (GetSelectionChangedHandler(d) == null)
{
SelectedCellsChangedEventHandler selectionchanged = (sender, e) =>
{
List<GridCell> cells = new List<GridCell>();
foreach (var selectedell in datagrid.SelectedCells)
{
string header = selectedell.Column.Header.ToString();
GridCell cell = new GridCell
{
RowIndex = datagrid.Items.IndexOf(selectedell.Item),
ColumnIndex = selectedell.Column.DisplayIndex,
Parent = selectedell.Item as ExpandoObject,
ColumnHeader = header,
Value = (selectedell.Item as IDictionary<string, object>)[header]
};
cells.Add(cell);
}
SetSelectedCells(d, cells);
};
SetSelectionChangedHandler(d, selectionchanged);
datagrid.SelectedCellsChanged += GetSelectionChangedHandler(d);
}
foreach (var selected in GetSelectedCells(d) as List<GridCell>)
{
DataGridCell actualCell = datagrid.GetCell(selected.RowIndex, selected.ColumnIndex);
actualCell.IsSelected = true;
actualCell.Focus();
}
}
}
for it to work i added some extention method to datagrid, to make it easier to get the Cell here the extention methodes: (stolen from this blog)
public static T GetVisualChild<T>(Visual parent) where T : Visual
{
T child = default(T);
int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < numVisuals; i++)
{
Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
child = v as T;
if (child == null)
{
child = GetVisualChild<T>(v);
}
if (child != null)
{
break;
}
}
return child;
}
public static DataGridCell GetCell(this DataGrid grid, int rowIndex, int columnIndex)
{
return GetCell(grid, GetRow(grid, rowIndex), columnIndex);
}
public static DataGridCell GetCell(this DataGrid grid, DataGridRow row, int column)
{
if (row != null)
{
DataGridCellsPresenter presenter = GetVisualChild<DataGridCellsPresenter>(row);
if (presenter == null)
{
grid.ScrollIntoView(row, grid.Columns[column]);
presenter = GetVisualChild<DataGridCellsPresenter>(row);
}
DataGridCell cell = (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(column);
return cell;
}
return null;
}
public static DataGridRow GetRow(this DataGrid grid, int index)
{
DataGridRow row = (DataGridRow)grid.ItemContainerGenerator.ContainerFromIndex(index);
if (row == null)
{
// May be virtualized, bring into view and try again.
grid.UpdateLayout();
grid.ScrollIntoView(grid.Items[index]);
row = (DataGridRow)grid.ItemContainerGenerator.ContainerFromIndex(index);
}
return row;
}