GIf图像不是动画

Question

我编写了以下代码来上传不同类型的图片。

public static void CompressImageWithNewDimensions(Stream stream, string targetPath, double fileSizeKB)
    {
        try
        {
            using (var image = Image.FromStream(stream))
            {
                double scaleFactor;
                if (fileSizeKB <= 900)
                {
                    scaleFactor = 0.9;
                }
                else if (fileSizeKB <= 1500)
                {
                    scaleFactor = 0.8;
                }
                else if (fileSizeKB <= 2000)
                {
                    scaleFactor = 0.7;
                }
                else
                {
                    scaleFactor = 0.3;
                }
                var newWidth = (int)(image.Width * scaleFactor);
                var newHeight = (int)(image.Height * scaleFactor);
                var CompressImage = new Bitmap(newWidth, newHeight);
                var CompressImageGraph = Graphics.FromImage(CompressImage);
                CompressImageGraph.CompositingQuality = CompositingQuality.HighQuality;
                CompressImageGraph.SmoothingMode = SmoothingMode.HighQuality;
                CompressImageGraph.InterpolationMode = InterpolationMode.HighQualityBicubic;
                var imageRectangle = new Rectangle(0, 0, newWidth, newHeight);
                CompressImageGraph.DrawImage(image, imageRectangle);
                //CompressImage.Save(targetPath, image.RawFormat);                    
                CompressImage.Save(targetPath, System.Drawing.Imaging.ImageFormat.Gif); 
            }
        }
        catch (Exception)
        {
        }
    }

现在我已经在我的文件夹中成功上传了GIF文件，但在我打开图片时的文件夹中，它不是动画。