private void loadCacheSize()
        {
            btnCache.Content = $"캐시 삭제 (계산중...)";

            var th = new Thread(() =>
            {
                var displaySize = "";

                var sizebyte = WebImage.GetCacheSize();
                if (sizebyte > 1024)
                {
                    float kb = sizebyte / 1024;

                    if (kb > 1024)
                    {
                        float mb    = kb / 1024;
                        displaySize = mb.ToString("0.0") + " mb";
                    }
                    else
                    {
                        displaySize = kb.ToString("0.0") + " kb";
                    }
                }
                else
                {
                    displaySize = sizebyte + " bytes";
                }

                Dispatcher.Invoke(new Action(() =>
                {
                    btnCache.Content = $"캐시 삭제 ({displaySize})";
                }));
            });

            th.Start();
        }