WPF TextBlock Text updates only once
===

Sorry for the possible noob question, I'm quite new to C# and WPF. 

I created a window with some controls on it. All of them have ToolTips filled out. I would like to have a dedicated area on the bottom of the window (a TextBlock) to show these tips instead of the tooltip ballons. I've already seen a solution for this, something similar:

    public partial class MyWindow : Window
    {
        public MyWindow()
        {
            InitializeComponent();

            EventManager.RegisterClassHandler(typeof(FrameworkElement), FrameworkElement.MouseEnterEvent, new MouseEventHandler(MyMouseEventHandler));
        }


        private void MyMouseEventHandler(object sender, MouseEventArgs e)
        {
            // To stop the tooltip from appearing, mark the event as handled
			// But not sure if it is really working
            e.Handled = true;

            FrameworkElement source = e.OriginalSource as FrameworkElement;
            if (null != source && null != source.ToolTip)
            {
                // This really disables displaying the tooltip. It is enough only for the current element...
                source.SetValue(ToolTipService.IsEnabledProperty, false);

				// Instead write the content of the tooltip into a textblock
                textBoxDescription.Text = source.ToolTip.ToString();
            }
        }


There is no databinding for the textblock, just plainly setting the text from code.

My problem is that this works fine on the first run, when the dialog is started with ShowDialog() method. But after closing (or hiding) and showing again __textBoxDescription__ does not update anymore. The event is raised and handled, I can see at debugging, that the control goes even to the line where the __textBoxDescription.Text__ is set, simply the TextBlock does not update anymore. I tried to replace the TextBlock with a TextBox, but same result.

Is there any way to force the TextBlock to update? Why do I need it? Why it works for the first time?

Many thanks in advance.