Sorting Nested ObservableCollection - windows-phone-7

Question

In my WP7 project i'm using nested Observable collection. However, my problem is sorting this nested collection by with its nested collection in descending order.
Data Structure of Collection:
public class SubCategory : INotifyPropertyChanged
{
private string _catName;
public string CatName
{
get { return _catName; }
set
{
_catName = value; NotifyPropertyChanged("CatName");
}
}
private ObservableCollection<ToDoList> _lists;
public ObservableCollection<ToDoList> Lists
{
get { return _lists; }
set
{
if (_lists != value)
{
_lists = value;
NotifyPropertyChanged("lists");
}
}
}
And this is the nested collection
public class ToDoList : INotifyPropertyChanged//, INotifyPropertyChanging
{
#region NotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
#endregion
#region NotifyPropertyChanging Members
// public event PropertyChangingEventHandler PropertyChanging;
/* private void NotifyPropertyChanging(string propertyName)
{
if (PropertyChanging != null)
PropertyChanging(this, new PropertyChangingEventArgs(propertyName));
}*/
#endregion
[Column(IsVersion = true)]
private Binary _version;
private int _ItemId;
[Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
public int ItemId
{
get { return _ItemId; }
set
{
if (_ItemId != value)
{
//NotifyPropertyChanging("ItemdId");
_ItemId = value;
NotifyPropertyChanged("ItemId");
}
}
}
private string _ItemTitle;
[Column]
public string ItemTitle
{
get { return _ItemTitle; }
set
{
if (_ItemTitle != value)
{
//NotifyPropertyChanging("ItemTitle");
_ItemTitle = value;
NotifyPropertyChanged("ItemTitle");
}
}
}
private double _ItemLatitude;
[Column]
public double ItemLatitude
{
get { return _ItemLatitude; }
set
{
if (_ItemLatitude != value)
{
//NotifyPropertyChanging("ItemLatitude");
_ItemLatitude = value;
NotifyPropertyChanged("ItemLatitude");
}
}
}
private string _ItemAddress;
[Column]
public string ItemAddress
{
get { return _ItemAddress; }
set
{
if (_ItemAddress != value)
{
//NotifyPropertyChanging("ItemAddress");
_ItemAddress = value;
NotifyPropertyChanged("ItemAddress");
}
}
}
private double _ItemLongtitude;
[Column]
public double ItemLongtitude
{
get { return _ItemLongtitude; }
set
{
if (_ItemLongtitude != value)
{
//NotifyPropertyChanging("ItemLongtitude");
_ItemLongtitude = value;
NotifyPropertyChanged("ItemLongtitude");
}
}
}
private string _ItemDescription;
[Column]
public string ItemDescription
{
get { return _ItemDescription; }
set
{
if (_ItemDescription != value)
{
//NotifyPropertyChanging("ItemDescription");
_ItemDescription = value;
NotifyPropertyChanged("ItemDescription");
}
}
}
private bool isScheduled;
[Column]
public bool IsScheduled
{
get { return isScheduled; }
set
{
if (isScheduled != value)
{
//NotifyPropertyChanging("IsScheduled");
isScheduled = value;
NotifyPropertyChanged("IsScheduled");
}
}
}
private string _reminderId;
[Column]
public String ReminderId
{
get { return _reminderId; }
set
{
if (_reminderId != value)
{
//NotifyPropertyChanging("ReminderId");
_reminderId = value;
NotifyPropertyChanged("ReminderId");
}
}
}
private String _ItemTime;
[Column]
public String ItemTime
{
get { return _ItemTime; }
set
{
if (_ItemTime != value)
{
//NotifyPropertyChanging("ItemTime");
_ItemTime = value;
NotifyPropertyChanged("ItemTime");
}
}
}
private bool _isComplete;
[Column]
public bool IsComplete
{
get { return _isComplete; }
set
{
if (_isComplete != value)
{
//NotifyPropertyChanging("IsComplete");
_isComplete = value;
NotifyPropertyChanged("IsComplete");
}
}
}
private char _importance;
[Column]
public char Importance
{
get { return _importance; }
set
{
if (_importance != value)
{
//NotifyPropertyChanging("Importance");
_importance = value;
NotifyPropertyChanged("Importance");
}
}
}
[Column]
internal int _categoryId;
private EntityRef<Category> _category;
public Category ToDoCategory
{
get { return _category.Entity; }
set
{
//NotifyPropertyChanging("ToDoCategory");
_category.Entity = value;
if (value != null)
{
_categoryId = value.CategoryId;
}
//NotifyPropertyChanging("ToDoCategory");
}
}
}

Answer 1

I solved by changing the get method. Here is how i did.
public ObservableCollection<ToDoList> Lists
{
get
{
var l = from ToDoList lis in _lists
orderby lis.ItemId descending
select lis;
return new ObservableCollection<ToDoList>(l);
}
set
{
if (_lists != value)
{
_lists = value;
NotifyPropertyChanged("lists");
}
}
}