CairoExplorer.FileToIconConverter.getImage C# (CSharp) Метод

        private BitmapSource getImage(string fileName, IconSize size)
        {
            Icon icon;
            string key = returnKey(fileName, size);
            string lookup = "aaa" + Path.GetExtension(fileName).ToLower();
            if (!key.StartsWith("."))
                lookup = fileName;

            if (isExecutable(fileName))
            {

                WriteableBitmap bitmap = new WriteableBitmap(addToDic("aaa.exe", size) as BitmapSource);
                System.Threading.ThreadPool.QueueUserWorkItem(new WaitCallback(PollIconCallback), new thumbnailInfo(bitmap, fileName, size));
                return bitmap;
            }

            else
                switch (size)
                {
                    case IconSize.thumbnail:
                        if (isImage(fileName))
                        {
                            //Load as jumbo icon first.                         
                            WriteableBitmap bitmap = new WriteableBitmap(addToDic(fileName, IconSize.jumbo) as BitmapSource);
                            //BitmapSource bitmapSource = addToDic(fileName, IconSize.jumbo) as BitmapSource;                            
                            //WriteableBitmap bitmap = new WriteableBitmap(256, 256, 96, 96, PixelFormats.Bgra32, null);
                            //copyBitmap(bitmapSource, bitmap, false);
                            System.Threading.ThreadPool.QueueUserWorkItem(new WaitCallback(PollThumbnailCallback), new thumbnailInfo(bitmap, fileName, size));
                            return bitmap;
                        }
                        else
                        {
                            return getImage(lookup, IconSize.jumbo);
                        }
                    case IconSize.jumbo:
                        return loadBitmap(loadJumbo(lookup));
                    case IconSize.extraLarge:
                        _imgList.ImageListSize = SysImageListSize.extraLargeIcons;
                        icon = _imgList.Icon(_imgList.IconIndex(lookup, isFolder(fileName)));
                        return loadBitmap(icon.ToBitmap());
                    default:
                        icon = GetFileIcon(lookup, size);
                        return loadBitmap(icon.ToBitmap());
                }
        }