How do I get DependencyProperty to work in Silverlight? - silverlight

Question

I'm trying to bind using a DependencyProperty, but I can't even get the DependencyProperty to work let alone try to bind to it.
I'm following a silverlight guide and up to this point I'm supposed to be able to set the property using XAML. Here is the code I have so far:
MainPage.xaml:
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:UserControlSample" x:Class="UserControlSample.MainPage"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400">
<Grid x:Name="LayoutRoot" Background="White">
<local:InfoRectangle Margin="32,36,0,0" HorizontalAlignment="Left" Height="70" VerticalAlignment="Top" Width="122" InfoText="New Text"/>
<local:InfoRectangle Margin="105,139,188,97" InfoText="some text" />
</Grid>
InfoRectangle.xaml:
<UserControl
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
mc:Ignorable="d"
x:Class="UserControlSample.InfoRectangle"
d:DesignWidth="122" d:DesignHeight="70">
<Grid x:Name="LayoutRoot">
<Rectangle Fill="#FFABABE9" Stroke="Black" RadiusY="4" RadiusX="4"/>
<TextBlock Name="InfoLabel" Text="Text block" Margin="5" />
</Grid>
InfoRectangle.xaml.cs:
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
namespace UserControlSample
{
public partial class InfoRectangle : UserControl
{
public InfoRectangle()
{
// Required to initialize variables
InitializeComponent();
}
public string InfoText
{
get { return (string)GetValue(InfoTextProperty); }
set { SetValue(InfoTextProperty, value); }
}
public static readonly DependencyProperty InfoTextProperty =
DependencyProperty.Register(
"InfoText",
typeof(string),
typeof(InfoRectangle),
new PropertyMetadata("something", InfoTextChanged));
private static void InfoTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
}
}
}
When I run the solution the two rectangles show up but they display just "Text block" which is neither the default set or the value set in the MainPage XAML for the user controls.

Answer 1

My answer in here details a nice compact example of a dependency property updating a given property on a view model. The property on your view model would be bound to your text block so once change notification fires, your text block should update.

Answer 2

Here is the solution;
It seems the callback method has to be completed.
private static void InfoTextChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
((InfoRectangle)d).InfoLabel.Text = e.NewValue.ToString();
}