ObservableCollection don't modify view - wpf

Question

I have strange WPF ObservableCollection behavior. By unclear reason when collection modified and there is another condition in getter-method in some property of my class, it does't modify View. Although CollectionChanged event was invoked!
Without condition in getter method collection works good.
Too complicated and long-winded to explain here what I do in my work project. Therefore I make small simplify project and emulate same behavior. This project show you problem better then thousand words.
To see the problem - launch project as it is, looks how it works. It is really simple, 2 radiobuttons, datagrid and nothing else. Then go to the MainWindowViewModel, GridItems-property, uncomment commented code and launch project again. See the difference. When collection modify, get-method of GridItems-property dont't invoke (I check it with debugger). How not invoked method can make affect on something??? I don't have any idea on it. Help plz.
Project link:
http://www.megafileupload.com/en/file/443850/ObservableCollection-zip.html
class MainWindowViewModel : ViewModelBase
{
private ObservableCollection<GridItem> _totalStorage;
private ObservableCollection<GridItem> _gridItems;
public ObservableCollection<GridItem> GridItems
{
get
{
//if (_gridItems.Count == 0)
//{
// return _totalStorage;
//}
return _gridItems;
}
set
{
_gridItems = value;
RaisePropertyChanged("GridItems");
}
}
public MainWindowViewModel()
{
_totalStorage = new ObservableCollection<GridItem>();
_gridItems = new ObservableCollection<GridItem>();
GridItemsInit();
_gridItems.CollectionChanged += CollectionChanged;
}
/// <summary>
/// Collection change event handler
/// </summary>
/// <param name="o"></param>
/// <param name="e"></param>
private void CollectionChanged(object o, NotifyCollectionChangedEventArgs e)
{
}
private void GridItemsInit()
{
_totalStorage.Add(new GridItem
{
Name = "Igor",
LastName = "Balachtin",
FilerField = FileStatusEnum.All
});
_totalStorage.Add(new GridItem
{
Name = "Misha",
LastName = "Ivanov",
FilerField = FileStatusEnum.All
});
_totalStorage.Add(new GridItem
{
Name = "Ahmed",
LastName = "Magamed",
FilerField = FileStatusEnum.All
});
_totalStorage.Add(new GridItem
{
Name = "abrek",
LastName = "cheburek",
FilerField = FileStatusEnum.All
});
_totalStorage.Add(new GridItem
{
Name = "Irka",
LastName = "Dirka",
FilerField = FileStatusEnum.All
});
}
private void RefreshGridSource(string statusParam)
{
_gridItems.Clear();
//Если нажали на баттон new
if (statusParam.Equals(FileStatusEnum.All.ToString()))
{
foreach (var item in _totalStorage)
{
_gridItems.Add(item);
}
}
//Если нажали на archived
else if (statusParam.Equals(FileStatusEnum.Filtered.ToString()))
{
foreach (var item in _totalStorage.Where(g => g.FilerField == FileStatusEnum.Filtered))
{
_gridItems.Add(item);
}
}
}
private RelayCommand<object> _radioCommand;
public RelayCommand<object> RadioCommand
{
get { return _radioCommand ?? (_radioCommand = new RelayCommand<object>(HandlerFileRadio)); }
}
private void HandlerFileRadio(object obj)
{
if (obj == null)
return;
var statusParam = obj.ToString();
RefreshGridSource(statusParam);
}
}
Look at this sample.
//if (_gridItems.Count == 0)
//{
// return _totalStorage;
//}
Model:
public enum FileStatusEnum
{
All = 0,
Filtered
}
public class GridItem
{
public String Name { get; set; }
public String LastName { get; set; }
public FileStatusEnum FilerField
{
get; set;
}
}
Xaml:
<Grid HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="3*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="0">
<RadioButton Margin="5" IsChecked="True" Command="{Binding RadioCommand}"
CommandParameter="All">All</RadioButton>
<RadioButton Margin="5" Command="{Binding RadioCommand}"
CommandParameter="Filtered">Filtered</RadioButton>
</StackPanel>
<DataGrid Grid.Column="1" ItemsSource="{Binding GridItems}" CanUserAddRows="False" AutoGenerateColumns="False">
<DataGrid.Columns>
<DataGridTextColumn Header="Name" Binding="{Binding Name}" IsReadOnly="True" />
<DataGridTextColumn Header="LastName" Binding="{Binding LastName}" IsReadOnly="True" />
</DataGrid.Columns>
</DataGrid>
</Grid>
really better post all code here instead of link? :/

Answer 1

Once you are changing record after that your property is not Notifying.so please Notify after changing the collection.
Add below line in RefreshGridSource method after collection changed .
RaisePropertyChanged("GridItems");

Answer 2

Your GridItems property can return either _totalStorage or _gridItems depending upon a condition; _totalStorage and _gridSettings are two different instances of ObservableCollection. Initially, when _gridItems has no items, your GridItems property returns _totalStorage to WPF, and WPF listens on this instance for any CollectionChanged events.
In your RefreshGridSource method you are updating _gridItems (a differnt instance from _totalStorage), which WPF has no knowledge of.
But, when you rasie property changed for GridItems property from RefreshGridSource method WPF will re-read the property GridItems - this time, WPF gets _gridItems collection and it works as you expected.
Hope, I have explained well enough.