private void OnEllipsis(object sender, SizeChangedEventArgs e)

         {

             FormattedText formattedText = new FormattedText(

                 this.Header.ToString(),

                 Thread.CurrentThread.CurrentCulture,

                 this.FlowDirection,

                 new Typeface(this.FontFamily, this.FontStyle, this.FontWeight, this.FontStretch),

                 this.FontSize,

                 this.Foreground);

             this.IsEllipsis = formattedText.Width > e.NewSize.Width;

         }