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// ObservableObject is a custom base class that implements INotifyPropertyChanged
internal class MainWindowVM : ObservableObject
{
private ObservableCollection<Item> mItems;
private HashSet<Item> mCheckedItems;
public IEnumerable<Item> Items { get { return mItems; } }
public string Text
{
get { return _text; }
set { Set(ref _text, value); }
}
private string _text;
public MainWindowVM()
{
mItems = new ObservableCollection<Item>();
mCheckedItems = new HashSet<Item>();
mItems.CollectionChanged += Items_CollectionChanged;
// Adding test data
for (int i = 0; i < 10; ++i)
{
mItems.Add(new Item(string.Format("Item {0}", i.ToString("00"))));
}
}
private void Items_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.OldItems != null)
{
foreach (Item item in e.OldItems)
{
item.PropertyChanged -= Item_PropertyChanged;
mCheckedItems.Remove(item);
}
}
if (e.NewItems != null)
{
foreach (Item item in e.NewItems)
{
item.PropertyChanged += Item_PropertyChanged;
if (item.IsChecked) mCheckedItems.Add(item);
}
}
UpdateText();
}
private void Item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "IsChecked")
{
Item item = (Item)sender;
if (item.IsChecked)
{
mCheckedItems.Add(item);
}
else
{
mCheckedItems.Remove(item);
}
UpdateText();
}
}
private void UpdateText()
{
switch (mCheckedItems.Count)
{
case 0:
Text = "<none>";
break;
case 1:
Text = mCheckedItems.First().Name;
break;
default:
Text = "<multiple>";
break;
}
}
}
// Test item class
// Test item class
internal class Item : ObservableObject
{
public string Name { get; private set; }
public bool IsChecked
{
get { return _isChecked; }
set { Set(ref _isChecked, value); }
}
private bool _isChecked;
public Item(string name)
{
Name = name;
}
public override string ToString()
{
return Name;
}
}
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