private void ThumbOnDragDelta(object sender, DragDeltaEventArgs e) { Thumb thumb = sender as Thumb; TextBlock textBlock = thumb.FindChild <TextBlock>("NValueTextBlock"); var videoSlider = _slider.FindVisualParent <VideoSlider>(); DateTime beginDateTime = new DateTime(); DateTime endDateTime = videoSlider.EndTime; double val = ((endDateTime - beginDateTime).TotalMilliseconds * _slider.Value) / 100; DateTime resTime = beginDateTime + TimeSpan.FromMilliseconds(val); videoSlider.Value = resTime; textBlock.Text = resTime.ToString("HH:mm:ss"); }