Question

I have the following sample code in WPF. It is working well when I put the xaml and corresponding C# code inside windows, but when I am using a user control, the databinding doesn’t work. why?

Here is the code:

User control XAML:

<UserControl x:Class="TestWpf.UserControl1"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
          xmlns:ec="clr-namespace:TestWpf"
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
<Grid x:Name="MainGrid" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
    <Grid.RowDefinitions>
        <RowDefinition Height="20"/>
        <RowDefinition Height="Auto"/>
        <RowDefinition  Height="*"/>
    </Grid.RowDefinitions>
    <WrapPanel HorizontalAlignment="Right"  VerticalAlignment="Stretch" Grid.Row="0" >
        <Button Content="Edit" HorizontalAlignment="Right"  Name="editButton1" VerticalAlignment="Stretch" Click="button1_Click" />
    </WrapPanel>
    <Grid x:Name="patientDataGrid" Margin="10,10,10,10" Grid.Row="1">
        <Grid.Resources>
            <Style TargetType="TextBox" >
                <Setter Property="IsEnabled" Value="{Binding Path=IsEditing, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ec:UserControl1}}}" />
            </Style>
        </Grid.Resources>
        <Grid.ColumnDefinitions>
            <ColumnDefinition />
            <ColumnDefinition />
            <ColumnDefinition />

        </Grid.ColumnDefinitions>
        <TextBox x:Name="textBox1"  Grid.Column="0" Text="!234" />
        <TextBox x:Name="textBox2"    Grid.Column="1" />
    </Grid>
</Grid>
</UserControl>

The user control C# code:

 public partial class UserControl1 : UserControl
 {
    public static readonly DependencyProperty IsEditingProperty = DependencyProperty.Register(
          "IsEditing", typeof(Boolean), typeof(MainWindow), new PropertyMetadata(false));

    public Boolean IsEditing
    {
        get { return (Boolean)GetValue(IsEditingProperty); }
        set { SetValue(IsEditingProperty, value); }
    }
    public UserControl1()
    {
        InitializeComponent();
    }
    private void button1_Click(object sender, RoutedEventArgs e)
    {
        IsEditing = !IsEditing;
    }
}

MainWindows XAML:

<Window x:Class="TestWpf.MainWindow"
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:ec="clr-namespace:TestWpf"
    Title="MainWindow" Height="200" Width="525">

    <ec:UserControl1 x:Name="c" />

</Window>

I notice that if I move all C# and xaml code from user control to MainWindows, the binding is working without any problem.

What is wrong with the code?

Answer 1

You registered the dependency property to be owned by MainWindow instead of your UserControl.

public static readonly DependencyProperty IsEditingProperty =
    DependencyProperty.Register
    (
        "IsEditing",
        typeof(Boolean),
        typeof(MainWindow), // <-- Here
        new PropertyMetadata(false)
    );