预览大尺寸图片的解决方案

System.Drawing.Image img = System.Drawing.Image.FromFile(photoPath);
            int width = Convert.ToInt32(img.Width);
            int height = Convert.ToInt32(img.Height);
            if (width > 400)
            {
                this.Image1.Width = 400;
            }
            this.Image1.ImageUrl = photoPath ;