public static ResourceDictionary GetAppResourceDictionary()
        {
            var assembly = Assembly.GetExecutingAssembly();
            string resourceDictionaryXaml;
            using (var appXamlResource = assembly.GetManifestResourceStream("Your.Namespace.Here.App.xaml"))
            {
                var appXamlBytes = new byte[appXamlResource.Length];
                appXamlResource.Read(appXamlBytes, 0, appXamlBytes.Length);
                var appXaml = Encoding.UTF8.GetString(appXamlBytes);
                resourceDictionaryXaml = appXaml.Replace("<Application.Resources>", string.Empty);
                resourceDictionaryXaml = resourceDictionaryXaml.Replace("</Application.Resources>", string.Empty);
                resourceDictionaryXaml = resourceDictionaryXaml.Replace("Application", "ResourceDictionary");
                resourceDictionaryXaml = resourceDictionaryXaml.Replace(
                    "\"clr-namespace:Your.Namespace.Here\"",
                    "\"clr-namespace:Your.Namespace.Here;assembly=YourAssembly\"");
                var xClassAttribute = string.Format("x:Class=\"{0}\"", (typeof(App)).FullName);
                resourceDictionaryXaml = resourceDictionaryXaml.Replace(xClassAttribute, string.Empty);
                var resourceDictionaryXamlBytes = Encoding.UTF8.GetBytes(resourceDictionaryXaml);
                using (var ms = new MemoryStream(resourceDictionaryXamlBytes))
                {
                    return (ResourceDictionary)XamlReader.Load(ms);
                }
            }
        }