Two way binding with converter without source modification - wpf

Question

I want to use linq grouping as itemssource for checkbox listview
It my data model:
public class GroupItem
{
public string name GroupName { get; set; }
public string boolean GroupItemFlag { get; set; }
}
It view model (data context):
...
IEnumerable<GroupItem> _groupItems;
public IEnumerable<IGrouping<string,GroupItem>> Groups
{
get { return _groupItems.GroupBy(__item=>__item.GroupName); }
}
...
it view:
...
<ListView ItemsSource={Binding Groups}>
<ListView.ItemTemplate>
<StackPanel Orientation="Horizontal">
<CheckBox IsChecked="{Binding Converter={StaticResource groupingToBooleanConverter}, Mode=TwoWay}"/>
<TextBlock Text="{Binding Key}"/>
</StackPanel>
</ListView.ItemTemplate>
</ListView>
...
groupingToBooleanConverter code:
public class GroupingToBooleanConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var group = value as IGrouping<string,GroupItem>;
return group.Any(__item => __item.GroupItemFlag);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
// problem here
// how to set for all group items GroupItemFlag=(bool)value;
}
}
I don't want create one more class "Group" for this, so i use IGrouping and converter.
May be I chose the wrong way?

Answer 1

You can achieve it even without converter:
<CheckBox IsChecked="{Binding Path=GroupItemFlag, Mode=OneWay}"
Command="{Binding DataContext.ToogleGroupCommand, ElementName=LayoutRoot}"
CommandParameter="{Binding}"/>
void ToogleGroupCommand_Execute(IGrouping<string, GroupItem> group){
bool newValue = !group.First().GroupItemFlag;
foreach(var item in group) item.GroupItemFlag = newValue;
}
if you are not using MVVM, then just handle Checked and Unchecked events.
However, if you are using MVVM, I highly recommend you to create Group class as ViVi suggests:
public MainViewModel()
{
Groups = _groupItems.GroupBy(i => i.GroupName).Select(i => new GroupViewModel(i.Key, i);
}
public Groups[] Groups {get;}
public class GroupViewModel
{
public GroupViewModel(string name, IEnumerable<GroupItem> items)
{
Items = items;
}
public string Name { get; }
public IEnumerable<GroupItem> Items { get; }
public bool? IsChecked
{
get
{
if (Items.All(i => i.GroupItemFlag)) return true;
if (Items.Any(i => i.GroupItemFlag)) return null;
return false;
}
set
{
foreach (var item in Items)
{
item.GroupItemFlag = value.GetValueOrDefault();
}
}
}
}