Silverlight - binding to control borderthickness - silverlight

Question

I'm trying to better understand Silverlights binding mechanism and so have created a simple program that will change the borderthickness of a listbox on the press of a button. However it doesn't work and I can't figure out what I am doing wrong. Any ideas?
XAML:
<Grid x:Name="LayoutRoot" Background="White">
<ListBox Height="100" HorizontalAlignment="Left" Margin="134,102,0,0" Name="listBox1" VerticalAlignment="Top" Width="120" BorderThickness="{Binding TheThickness, Mode=TwoWay}" />
<Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="276,36,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
</Grid>
Code:
using System.ComponentModel;
using System.Windows;
using System.Windows.Controls;
namespace SilverlightApplication4
{
public partial class MainPage : UserControl
{
private TestClass testInst = new TestClass();
public MainPage()
{
InitializeComponent();
listBox1.DataContext = testInst;
}
private void button1_Click(object sender, RoutedEventArgs e)
{
testInst.TheThickness = 10;
}
}
public class TestClass
{
private int theThickness = 5;
public int TheThickness
{
get { return theThickness; }
set
{
theThickness = value;
NotifyPropertyChanged("TheThickness");
}
}
public event PropertyChangedEventHandler PropertyChanged;
// NotifyPropertyChanged will raise the PropertyChanged event, passing the source property that is being updated.
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
}

Answer 1

A border thickness is of Type Thickness which has multiple values for Top, Bottom, Left and Right. The XAML parser knows how to handle something like BorderThickness="5" correctly but in code you need to use the Thickness type. For example:-
public Thickness SelectedThickness
{
get { return (Thickness)GetValue(SelectedThicknessProperty); }
set { SetValue(SelectedThicknessProperty, value); }
}
public static readonly DependencyProperty SelectedThicknessProperty =
DependencyProperty.Register("SelectedThickness", typeof(Thickness), typeof(MyRectangle),
new PropertyMetadata(new Thickness() { Top = 1, Bottom = 1, Left = 1, Right = 1 }));
}
In this case the default Thickness of 1.
Edit Code more like yours:-
private Thickness theThickness = new Thickness() {Left = 5, Right = 5, Top = 5, Bottom = 5};
public Thickness TheThickness
{
get { return theThickness; }
set
{
theThickness = value;
NotifyPropertyChanged("TheThickness");
}
}