asp.net 上传图片并生成缩略图

    bool fileOK = false;
        string path = Server.MapPath("~/Upload")+"\\";      //上传路径
        if (fupImgUrl.HasFile)
        {
            string fileExtension = System.IO.Path.GetExtension(fupImgUrl.FileName).ToLower();　　　//获取要上传文件的扩展名

            string[] allowedExtensions ={ ".gif", ".png", ".jpeg", ".jpg" };
            for (int i = 0; i < allowedExtensions.Length; i++)
            {
                if (fileExtension == allowedExtensions[i])
                {
                    fileOK = true;
                }
            }
        }

        string fileName = DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + DateTime.Now.Day.ToString() +DateTime.Now.Hour.ToString()+ DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + System.IO.Path.GetExtension(fupImgUrl.FileName).ToLower();　　　//生成随机的文件名
        if (fileOK)
        {
            try
            {
                fupImgUrl.PostedFile.SaveAs(path + fileName);　　//上传原图
                System.Drawing.Image image, sImage;
                image = System.Drawing.Image.FromStream(fupImgUrl.PostedFile.InputStream);
                int width = image.Width;
                int height = image.Height;
                int NewWidth, NewHeight;
                if (width > height)
                {
                    NewWidth = 150;
                    NewHeight = NewWidth*height / width;
                }
                else
                {
                    NewHeight = 150;
                    NewWidth = NewHeight*width / height;
                }
                sImage = image.GetThumbnailImage(NewWidth, NewHeight, null, IntPtr.Zero);
                int x, y;
                x = sImage.Width / 2 - 30;
                y = sImage.Height - 20;
                System.Drawing.Bitmap output = new System.Drawing.Bitmap(sImage);
                System.Drawing.Graphics g= System.Drawing.Graphics.FromImage(output);
                System.Drawing.Font Fonts = new System.Drawing.Font("Courier New", 9);
                g.DrawString("水印内容。。。。", Fonts, new System.Drawing.SolidBrush(System.Drawing.Color.Red), x, y);
                output.Save(path + "s\\" + fileName, System.Drawing.Imaging.ImageFormat.Jpeg);

                Response.Write("<script>alert('上传文件成功')</script>");
                lbFileName.Text ="~/upload/"+fileName;
                lbImages.Text = "~/upload/s/" + fileName;
            }
            catch (Exception ex)
            {
                Response.Write("<script>alert('"+ex.Message+"')</script>");
            }
        }
        else
        {
            Response.Write("<script>alert('无效的文件类型')</script>");
        }