Binding Silverlight UserControl custom properties to its' elements

Question

I'm trying to make a simple crossword puzzle game in Silverlight 2.0. I'm working on a UserControl-ish component that represents a square in the puzzle. I'm having trouble with binding up my UserControl's properties with its' elements. I've finally (sort of) got it working (may be helpful to some - it took me a few long hours), but wanted to make it more 'elegant'.

I've imagined it should have a compartment for the content and a label (in the upper right corner) that optionally contains its' number. The content control probably be a TextBox, while label control could be a TextBlock. So I created a UserControl with this basic structure (the values are hardcoded at this stage):

    <UserControl x:Class="XWord.Square"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    FontSize="30" 
    Width="100" Height="100">
        <Grid x:Name="LayoutRoot" Background="White">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="Auto"/>
            </Grid.ColumnDefinitions>

            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>

            <TextBlock x:Name="Label" Grid.Row="0" Grid.Column="1" 
                Text="7"/>
            <TextBox x:Name="Content" Grid.Row="1" Grid.Column="0"  
                Text="A"
                BorderThickness="0" />

        </Grid>
    </UserControl>

I've also created DependencyProperties in the Square class like this:

     public static readonly DependencyProperty LabelTextProperty;
     public static readonly DependencyProperty ContentCharacterProperty;

     // ...(static constructor with property registration, .NET properties
     // omitted for brevity)...

Now I'd like to figure out how to bind the Label and Content element to the two properties. I do it like this (in the code-behind file):

     Label.SetBinding( TextBlock.TextProperty, new Binding { Source = this, Path = new PropertyPath( "LabelText" ), Mode = BindingMode.OneWay } );
     Content.SetBinding( TextBox.TextProperty, new Binding { Source = this, Path = new PropertyPath( "ContentCharacter" ), Mode = BindingMode.TwoWay } );

That would be more elegant done in XAML. Does anyone know how that's done?

Answer 1

First, set the DataContext on the UserControl using {RelativeSource Self}:

<UserControl x:Class="XWord.Square"  
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"   
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"  
FontSize="30"   
Width="100" Height="100" 
DataContext="{Binding RelativeSource={RelativeSource Self}}">

Now you can bind the individual elements to the properties of the usercontrol:

<TextBlock x:Name="Label" Grid.Row="0" Grid.Column="1" 
Text="{Binding LabelText}"/>  
<TextBox x:Name="Content" Grid.Row="1" Grid.Column="0" 
Text="{Binding ContentCharacter}" BorderThickness="0" />

For SL 2.0, you'll need to set the DataContext on the UserControl's Loaded event handler.

private void UserControl_Loaded( object sender, RoutedEventArgs e ) {
    LayoutRoot.DataContext = this;
}

Answer 2

As Silverlight cannot use FindAncestor technique you can use a trick similar to the one that sets the UserControl's name, but without breaking its functionality by using the name of the LayoutRoot...

<UserControl x:Class="XWord.Square"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
FontSize="30" 
Width="100" Height="100">
    <Grid x:Name="LayoutRoot" Background="White">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="Auto"/>
        </Grid.ColumnDefinitions>

        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <TextBlock x:Name="{Binding Path=Parent.LabelText, ElementName=LayoutRoot}" Grid.Row="0" Grid.Column="1" 
            Text="7"/>
        <TextBox x:Name="{Binding Path=Parent.ContentCharacter, ElementName=LayoutRoot}" Grid.Row="1" Grid.Column="0"  
            Text="A"
            BorderThickness="0" />
    </Grid>
</UserControl>

It worked in SL3 without having to add any additional code (I'm using it in a WP7 app), but don't know if you can use it in SL2. Well, I realize now how this question is old, hope it's still helpful, I've arrived here because the answers I got for the same problem in WP7 didn't convince me.