Issue with DataBinding on a UserControl

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.NET3.5

.NET

WPF

I am in a very basic problem.
I have created a user control, say sample like this :

<UserControl x:Class="TextCalc.txtItem"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Grid>
        <TextBox Name="txtMessage" Text="{Binding Message, ElementName=root}" Width="30" Height="20"></TextBox>
    </Grid>
</UserControl>

I have created a DependencyProperty named Message which I want to work with DataBinding. The Code looks like :

public partial class txtItem : UserControl
{
public static readonly DependencyProperty MessageProperty = DependencyProperty.Register("Message",typeof(String),typeof(txtItem), new UIPropertyMetadata("0", textChangedCallback));
        private static void textChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            txtItem input = (txtItem)d;
            input.txtMessage.Text = e.NewValue as String;
        }
        public string Message
        {
            get { return (string)GetValue(MessageProperty); }
            set { SetValue(MessageProperty, value); }
        }
 }

Now once I built the control, I want this control to work with Databinding just like how normal TextBox works. In my Window, I used this as :

<ListBox x:Name="lstBox" ItemsSource="{Binding}">
           <ListBox.ItemTemplate>
               <DataTemplate>
                   <StackPanel Orientation="Horizontal">
                       <TextBlock Text="{Binding Name}" />
                       <local:txtItem HorizontalAlignment="Center" VerticalAlignment="Center"  Width="50" Message="{Binding Value}"/>
                   </StackPanel>
               </DataTemplate>
           </ListBox.ItemTemplate>
       </ListBox>

From the codebehind :
private List<Element> items = null;

private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            this.items = new List<Element>();
            items.Add(new Element { Name = "Abhishek", Value = "300" });
            this.lstBox.DataContext = items;
        }

The Element class is also implemented from INotifyPropertyChanged :

public class Element : INotifyPropertyChanged
    {
        private string _Name;
        public string Name
        {
            get
            {
                return this._Name;
            }
            set
            {
                this._Name = value;
                this.OnPropertyChanged("Name");
            }
        }
        private string _Value;
        public string Value
        {
            get
            {
                return this._Value;
            }
            set
            {
                this._Value = value;
                this.OnPropertyChanged("Value");
            }
        }

        #region INotifyPropertyChanged Members
        public virtual void OnPropertyChanged(string info)
        {
            if(this.PropertyChanged != null)
                this.PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
        public event PropertyChangedEventHandler PropertyChanged;
        #endregion
    }

Now when I change the data within the Textbox that comes within the UserControl, it doesnt update the actual object. I have even implemented the UserControl from INotifyPropertyChanged, and invoked the event when the value is changed on the TextBox, but alas, it didnt worked for me. Can anyone help me in this regard.

If you want to see the code you can download from here:
TextCalc.zip (80 KB)