private static void Warmup(MarkupExtensionParser markupExtensionParser, string defaultCssNamespace) { // warmup parser markupExtensionParser.Parse("true", Application.Current?.MainWindow ?? new FrameworkElement(), new[] { new CssNamespace("", defaultCssNamespace) }); TypeHelpers.GetPropertyAccessor(typeof(FrameworkElement), "IsLoaded"); var styleSheet = CssParser.Parse("*{Background: #DynamicResource no;}"); var f = new Button(); f.SetValue(Css.StyleSheetProperty, styleSheet); f.Content = new TextBlock(); instance.EnqueueNewElement(f, styleSheet, f); instance.ExecuteApplyStyles(); }