New Post: Basic RichTextBox usage - .Text Property does not update

Xaml:
<StackPanel>

<xctk:RichTextBox x:Name="_richTextBox" Text="{Binding Path=Content,Mode=TwoWay}" Width="200"/>
    <Button Content="Click Me" Click="Button_Click" />
</StackPanel> 

Code-Behind:

public partial class MainWindow : Window
{
    private Book book;
    public MainWindow()
    {
        InitializeComponent();
        book = new Book();
        this.DataContext = book;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        _richTextBox.Document.Blocks.Add(new Paragraph(new Run("english")));//statement 1

        System.Diagnostics.Debug.WriteLine("Text is now : " + _richTextBox.Text);
    }
}

public class Book: INotifyPropertyChanged {
    private string content;
    public string Content {
        get
        {
            return content;
        }
        set
        {
            content = value;
            OnPropertyChanged("Content");
        }
    }

    public event System.ComponentModel.PropertyChangedEventHandler PropertyChanged;

    protected void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
            PropertyChanged(this,
                new System.ComponentModel.PropertyChangedEventArgs(propertyName));
    }
} 

When we input some text from the interface,the book.Content gets changed immediately.While if we modify the Document from the code behind(statement 1),the Content doesn't change.If I put some code,like I have mentioned before, behind the statement 1 :

_richTextBox.SetValue(Xceed.Wpf.Toolkit.RichTextBox.TextProperty, _richTextBox.TextFormatter.GetText(_richTextBox.Document));
_richTextBox.RaiseEvent(new System.Windows.RoutedEventArgs(System.Windows.UIElement.LostFocusEvent, _richTextBox));

It is ok now.

Sincerely Yours.