Question

I have a user control that I’m using across several pages which defines a header label and two buttons. I want the control to be able to have child controls, but I ran into the problem of binding those child controls since they are in an itemscollection. When I add bindings to the child controls in XAML they are not registered.

Error output: System.Windows.Data Error: 4 : Cannot find source for binding with reference 'ElementName=MyPage'. BindingExpression:Path=MyText; DataItem=null; target element is 'TextBox' (Name=''); target property is 'Text' (type 'String')

Excess code omitted for brevity.

e.g.

XAML

<UserControl x:Class="MyControl" Name="MyControl">
    <Grid>
        <ItemsControl Name="ItemsControl" ItemsSource="{Binding ItemsSource, ElementName=MyControl}" />
    </Grid>
</UserControl>

Code Behind

[ContentProperty("Items")]
public partial class MyControl : UserControl
{
    public static readonly DependencyProperty ItemsSourceProperty =
            ItemsControl.ItemsSourceProperty.AddOwner(typeof (MyControl));

    public IEnumerable ItemsSource
    {
        get { return (IEnumerable) GetValue(ItemsSourceProperty); }
        set { SetValue(ItemsSourceProperty, value); }
    }

    public ItemCollection Items
    {
        get { return ItemsControl.Items; }
    }
}

Usage:

<Page x:Class="MyPage" Name="MyPage">
    <MyControl>
        <TextBox Text="{Binding MyText,
                        ElementName=MyPage,
                        UpdateSourceTrigger=PropertyChanged}" />
    </MyControl>
</Page>

Code Behind

public partial class MyPage : Page, INotifyPropertyChanged
{
    private string _myText;
    public string MyText
    {
        get{ return _myText; }
        set
        {
            _myText = value;
            OnPropertyChanged("MyText");
        }
    }
}

I would like to be able to databind the TextBox to the MyText property so that whenever I modify it in the code behind it will get updated on the page.

Answer 1

Converting my comment into an answer:

remove the ElementName and try RelativeSource={RelativeSource FindAncestor, AncestorType=Page}