从wpf中未引用的dll加载图像

我使用wpf开发应用程序，它可以使用多种语言。用户可以将语言dll放在Languages文件夹中，并动态加载程序。我想显示带有国家标志的程序集名称。我写了这个代码，但标志图像没有显示在组合框中。我该怎么做？

        var assemblies = dir.GetFiles("*.dll", SearchOption.AllDirectories);
        //for each found .dll we will create a model and set its properties and then add to list
        for (int i = 0; i < assemblies.Count(); i++)
        {
            var assemblyName = assemblies[i].Name.Substring(0, assemblies[i].Name.LastIndexOf("."));
            string packUri = string.Format("pack://application:,,,/{0};component/Image/flag.png", assemblyName);
            Uri uri = new Uri(packUri, UriKind.Absolute);
            BitmapImage image = new BitmapImage();
            image.BeginInit();
            image.CacheOption = BitmapCacheOption.OnLoad;
            try
            {
                image.UriSource = uri;
                image.EndInit();
            }
            catch (Exception ex)
            {
                var m = ex.Message;
            }
            CultureAssemblyModel model = new CultureAssemblyModel()
            {
                DisplayText = assemblies[i].Name.Split('.', '_')[2],
                Culture = assemblies[i].Name.Split('.', '_')[1],
                Name = assemblies[i].Name,
                XamlFileName = assemblies[i].Name.Substring(0,                      assemblies[i].Name.LastIndexOf(".")) + ".xaml",FlagImage=image
            };