How to force datasource to be updated from TemplateControl - wpf

Question

I broke my head by solving a simple problem. I have a custom control with filled Template property. The template is a simple Grid with a TextBox inside. This text box is bound to a singleton's proprty with setter and getter. How can I programmatically force the TextBox to read value from the singleton and put it back?
<Window x:Class="Spike.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="305" Width="521" xmlns:my="clr-namespace:Spike" xmlns:Data="clr-namespace:Spike.Data">
<Grid>
<Grid.Resources>
<ControlTemplate x:Key="editingTemplate">
<Grid>
<TextBox Text="{Binding Source={x:Static Data:MyClass.Instance}, Path=Value2}"/>
</Grid>
</ControlTemplate>
</Grid.Resources>
<UserControl Template="{StaticResource editingTemplate}" HorizontalAlignment="Left" Margin="58,60,0,0" x:Name="myUserControl1" VerticalAlignment="Top" Height="75" Width="284" />
<Button Content="Update source" Height="23" HorizontalAlignment="Left" Margin="184,23,0,0" Name="button1" VerticalAlignment="Top" Width="111" Click="button1_UpdateSource" Focusable="False" />
<Button Content="Update control" Focusable="False" Height="23" HorizontalAlignment="Left" Margin="58,23,0,0" Name="button2" VerticalAlignment="Top" Width="111" Click="button2_UpdateControl" />
</Grid>
</Window>
namespace Spike.Data
{
public class MyClass
{
private static readonly MyClass MyClassInstance = new MyClass();
public MyClass()
{
Value1 = "value1";
Value2 = "value2";
}
public static MyClass Instance
{
get { return MyClassInstance; }
}
public string Value1 { get; set; }
public string Value2 { get; set; }
}
}
In other words what should be implemented in button2_UpdateControl and button1_UpdateSource methods?
Thank you in advance for any help

Answer 1

A Binding shouldn't be re-invoked manually. Instead, you should try and make your current Binding mechanism work properly.
Your TextBox should bind to DependancyProperty or the DataContext of the TextBox should implement INotifyPropertyChanged.
Define your Value2 property like this:
public static readonly DependencyProperty Value2Property =
DependencyProperty.Register("Value2", typeof(string), typeof(MyClass), new PropertyMetadata(string.Empty));
public string Value2
{
get { return (string)GetValue(Value2Property); }
set { SetValue(Value2Property, value); }
}
Also, MyClass should implement UIElement.