AcManager.Pages.Windows.MainWindow.OnLoaded C# (CSharp) Method

        private void OnLoaded(object sender, RoutedEventArgs e) {
            if (_loaded) return;
            _loaded = true;

            AboutHelper.Instance.PropertyChanged += About_PropertyChanged;
            UpdateAboutIsNew();

            var background = AppArguments.Get(AppFlag.Background);
            if (string.IsNullOrWhiteSpace(background)) {
                FancyBackgroundManager.Instance.AddListener(this);
            } else {
                if (background.ElementAt(1) != ':') {
                    background = System.IO.Path.Combine(FilesStorage.Instance.GetDirectory("Themes", "Backgrounds"), background);
                }

                var animatedBackground = Regex.IsMatch(background, @"\.(?:avi|flv|gif|m(?:4[pv]|kv|ov|p[4g])|og[vg]|qt|webm|wmv)$", RegexOptions.IgnoreCase) ?
                        background : null;
                var staticBackground = animatedBackground == null ? background : Regex.Replace(background, @"\.\w+$", @".jpg");
                
                BackgroundContent = new Viewbox {
                    Stretch = Stretch.UniformToFill,
                    Opacity = AppArguments.GetDouble(AppFlag.BackgroundOpacity, 0.5),
                    VerticalAlignment = VerticalAlignment.Center,
                    HorizontalAlignment = HorizontalAlignment.Center,
                    Child = new DynamicBackground {
                        Width = 1280,
                        Height = 720,
                        Animated = animatedBackground,
                        Static = staticBackground
                    }
                };
            }
        }