You will have to listen CollectionChanged of ItemInfo like
public class Order : INotifyPropertyChangedBase
{
public Order()
{
ItemInfo =new ObservableCollection<Item>();
ItemInfo.CollectionChanged += ItemInfo_CollectionChanged;
}
void ItemInfo_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
OnPropertyChanged("TotalPrice");
}
private ObservableCollection<Item> itemInfo;
public ObservableCollection<Item> ItemInfo
{
get { return itemInfo; }
set
{
itemInfo = value;
OnPropertyChanged("ItemInfo");
OnPropertyChanged("TotalPrice");
}
}
OR
public class Order : INotifyPropertyChangedBase
{
void ItemInfo_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
{
OnPropertyChanged("TotalPrice");
}
private ObservableCollection<Item> itemInfo;
public ObservableCollection<Item> ItemInfo
{
get { return itemInfo; }
set
{
if(itemInfo!=null)
itemInfo.CollectionChanged -= ItemInfo_CollectionChanged;
itemInfo = value;
if(itemInfo!=null)
itemInfo.CollectionChanged += ItemInfo_CollectionChanged;
OnPropertyChanged("ItemInfo");
OnPropertyChanged("TotalPrice");
}
}