AncestorBinding & ItemsControlBinding

These markup extensions provide relative binding based on ancestor type. If you are familiar with WPF, they are very similar to {RelativeSource Mode=FindAncestor}. They are typically used from inside a DataTemplate to access elements outside of said data-template which is not normally accessible (eg: through ElementName binding). The common usage is to access the parent data-context from inside the ItemsControl.ItemTemplate.

Remarks

Both of the markup extensions are available for all non-Windows UWP platforms as well as all WinUI 3 platforms.

ItemsControlBinding

This markup extension provides a binding to the closest parent ItemsControl. This markup can be used to access the parent ItemsControl from inside of the ItemTemplate.

Tip

This is a shortcut for {utu:AncestorBinding AncestorType=ItemsControl}.

Properties

Property	Type	Description
Path	string	Binding path from the ancestor.

Usage

public class ExampleModel
{
    public int[] Items { get; } = new[] { 1, 2, 3 };
    public string SomeText { get; } = "Lorem Ipsum";
}

<!-- Include the following XAML namespace to use the samples below -->
xmlns:utu="using:Uno.Toolkit.UI"
...

<!-- Assuming the DataContext is set to an instance of ExampleModel -->
<ListView ItemsSource="{Binding Items}">
    <ListView.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBlock>Current item DataContext: <Run Text="{Binding}" /></TextBlock>
                <TextBlock>Current parent(ExampleModel) DataContext:
                    <Run Text="{utu:ItemsControlBinding Path=DataContext.SomeText}" />
                </TextBlock>
            <StackPanel>
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>

AncestorBinding

This markup extension provides a means to bind to an ancestor of a specific type.

Properties

Property	Type	Description
AncestorType	Type	Type of ancestor to bind from.
Path	string	Binding path from the ancestor.

Usage

public class ExampleModel
{
    public int[] Items { get; } = new[] { 1, 2, 3 };
    public string SomeText { get; } = "Lorem Ipsum";
}

<!-- Include the following XAML namespace to use the samples below -->
xmlns:utu="using:Uno.Toolkit.UI"
...

<!-- Assuming the DataContext is set to an instance of ExampleModel -->
<Border Tag="From Border">
    <ListView ItemsSource="{Binding Items}" Tag="From ListView">
        <ListView.ItemTemplate>
            <DataTemplate>
                <StackPanel>
                    <TextBlock>Current item DataContext: <Run Text="{Binding}" /></TextBlock>
                    <TextBlock>Current parent(ExampleModel) DataContext:
                        <Run Text="{utu:AncestorBinding AncestorType=ListView, Path=DataContext.SomeText}" />
                    </TextBlock>

                    <TextBlock>Accessing property of a parent ListView:
                        <Run Text="{utu:AncestorBinding AncestorType=ListView, Path=Tag}" />
                    </TextBlock>
                    <TextBlock>Accessing property of a parent Border:
                        <Run Text="{utu:AncestorBinding AncestorType=Border, Path=Tag}" />
                    </TextBlock>
                <StackPanel>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>
</Border>