public class MyTheme {
        public ResourceDictionary Dictionary { get; set; }

        public MyTheme() {
            string content;

            using (StreamReader sr = new StreamReader(
                Application.GetResourceStream(new Uri("/TelerikTheme;component/Styles/Generic.xaml", UriKind.Relative)).Stream)) {
                content = sr.ReadToEnd();
                sr.Close();
            }

            this.Dictionary = XamlReader.Load(content) as ResourceDictionary;
        }
    }

            Application.Current.Resources.MergedDictionaries.Add(new MyTheme().Dictionary);