Forward Binding i.e. reapply a binding

Lars Larsson 31

Is it possible to create an attached property containing a Binding/BindingBase & then apply it to a control i.e. forward a binding thru XAML.

Example would be you can have global style that use attached properties & then local styles to set them or retrieve from parents. Example would be to control IsExpanded in DataGrid GroupItem by expressing the "binding" somewhere else & then apply it to the control. This includes controlling mode=two-way or one-way.

One example would be if binding results in a binding that is applied. Any good way or somehow using markup-extensiosn?

Hui Liu-MSFT 41,146 Microsoft Vendor

Hi,@Lars Larsson. Welcome Microsoft Q&A. Could you share with me the code that reproduces your problem for analysis? Or can you describe the specific implementation you want with some code or pictures? Does the following example result resemble what you want?

 <Grid>
        <DataGrid    ItemsSource="{Binding ResultColl}"  AutoGenerateColumns="False"    SelectedItem="{Binding Path=SelectedResultItem, Mode=TwoWay}" SelectionMode="Single" IsReadOnly="True" >
            <DataGrid.GroupStyle>
                <GroupStyle>
                    <GroupStyle.ContainerStyle>
                        <Style TargetType="{x:Type GroupItem}">
                            <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="{x:Type GroupItem}">
                                        <Expander  IsExpanded="{Binding Items[0].IsExpanded}">
                                            <Expander.Header>
                                                <StackPanel>
                                                    <TextBox Text="{Binding Items[0].ID}" />
                                                </StackPanel>
                                            </Expander.Header>
                                            <ItemsPresenter />
                                        </Expander>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                        </Style>
                    </GroupStyle.ContainerStyle>
                </GroupStyle>
            </DataGrid.GroupStyle>

            <DataGrid.Columns>
                <DataGridTextColumn Header="ID" Binding="{Binding Path=ID}"/>
                <DataGridTextColumn Header="Typ"  Binding="{Binding Path=Typ}"/>
                <DataGridTextColumn Header="Info"  Binding="{Binding Path=Info}"/>
                <DataGridTextColumn Header="orderDate"  Binding="{Binding Path=orderDate, StringFormat={}{0:dd-MM-yyyy}}"/>
            </DataGrid.Columns>
        </DataGrid>

    </Grid>

Codebedhind:

public partial class MainWindow : Window  , INotifyPropertyChanged
    {
        public MainWindow()
        {
            InitializeComponent();
            for(int i = 1; i < 10; i++)
            {
                myList.Add(new ItemResult() { ID = "1", Typ = $"A{i}", Info = "Info " + i.ToString(), orderDate = DateTime.Now.AddDays(i) });
                myList.Add(new ItemResult() { ID = "2", Typ = $"B{i}", Info = "Info " + i.ToString(), orderDate = DateTime.Now.AddDays(i) });
            }
            ListCollectionView tmp = new ListCollectionView(myList);
            tmp.GroupDescriptions.Add(new PropertyGroupDescription("ID"));
            ResultColl = tmp;
            DataContext= this;
        }
        private ObservableCollection<ItemResult> myList = new ObservableCollection<ItemResult>();
        public ObservableCollection<ItemResult> MyList
        {
            get { return myList; }
            set
            {
                if (myList != value)
                {
                    myList = value;
                    OnPropertyChanged("MyList");
                }
            }
        }
        private ItemResult _selectedResultItem;
        public ItemResult SelectedResultItem
        {
            get { return _selectedResultItem; }
            set
            {
                _selectedResultItem = value;
                OnPropertyChanged("SelectedResultItem");
            }
        }
        private ListCollectionView _resultColl;
        public ListCollectionView ResultColl
        {
            get { return _resultColl; }
            set
            {
                _resultColl = value;

                OnPropertyChanged("ResultColl");
                if (value != null && _resultColl.Count > 0)
                    SelectedResultItem = _resultColl.GetItemAt(0) as ItemResult;
            }
        }
        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged([CallerMemberName] string name = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));
        }
    }
    public class ItemResult
    {
        public string ID { get; set; }
        public string Typ { get; set; }
         public string Info { get; set; }
        public DateTime orderDate { get; set; }

    }

The result:

Lars Larsson 31

<Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type GroupItem}" >
                    <Expander Margin="1" BorderBrush="{StaticResource GrayDark}" Style="{StaticResource ExpanderStyleSmaller}" 
                      IsExpanded="{f:ApplyBindingMarkup {Binding Path=(f:GroupItem.IsExpandedBinding), RelativeSource={RelativeSource TemplatedParent}}, FallbackValue={StaticResource True}}" 
                      Validation.ErrorTemplate="{x:Null}" >                 Validation.ErrorTemplate="{x:Null}" >

public static readonly DependencyProperty IsExpandedBindingProperty =
           DependencyProperty.RegisterAttached("IsExpandedBinding", typeof(BindingBase), typeof(GroupItem), new PropertyMetadata(null));

I thought I could reuse Binding (but didn't find that I had or any way to do it). But I am curious if some way to do it easily i.e. I hope the concept is clear & ApplyBindingMarkup was just attempt to see I could do something there.

Wanted to see if I could consolide styles - to much copy paste & made more sense to try use for

GroupStyle.HeaderTemplate

Would be quite convinent if one could tunnel/forward bindings for extending behaviors generally while maintaining control at root xaml level.

Hui Liu-MSFT 41,146 Reputation points Microsoft Vendor

2023-09-28T09:42:42.02+00:00

Hi,@Lars Larsson. If you're looking for a way to consolidate styles and possibly reuse bindings within a ControlTemplate for a GroupItem. Unfortunately, there isn't a direct way to reuse bindings in the way you've described in XAML. Bindings are meant to be defined directly on individual elements.
The question is not very clear, please clarify your question. It would be great if you could share a complete example sample where I can reproduce the problem and describe the expected results you want to achieve to analyze.

1 answer

Lars Larsson 31 Reputation points

2023-09-28T10:10:38.24+00:00

Guess that is the answer - no easy or native way to reuse except maybe building with attached behavior or other messy/specific fuzzy code.
Would have been nice to use nested binding / apply a binding found using a binding.
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Forward Binding i.e. reapply a binding

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