Asp.net(C#)給圖片加上浮水印效果

下面的代碼中，加文字浮水印和加圖片浮水印的代碼不能共存
我是為了方便顯示才寫在一塊的

    private void Btn_Upload_Click(object sender, System.EventArgs e)
        {
            if(UploadFile.PostedFile.FileName.Trim()!="")
            {
                //上傳檔案
                string extension = Path.GetExtension(UploadFile.PostedFile.FileName).ToUpper();
                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();
                string path = Server.MapPath(".") + "/UploadFile/" + fileName + extension;
                UploadFile.PostedFile.SaveAs(path);

                //加文字浮水印，注意，這裡的代碼和以下加圖片浮水印的代碼不能共存
                System.Drawing.Image image = System.Drawing.Image.FromFile(path);
                Graphics g = Graphics.FromImage(image);
                g.DrawImage(image, 0, 0, image.Width, image.Height);
                Font f = new Font("Verdana", 32);
                Brush b = new SolidBrush(Color.White);
                string addText = AddText.Value.Trim();
                g.DrawString(addText, f, b, 10, 10);
                g.Dispose();

                //加圖片浮水印
                System.Drawing.Image image = System.Drawing.Image.FromFile(path);
                System.Drawing.Image copyImage = System.Drawing.Image.FromFile( Server.MapPath(".") + "/Alex.gif");
                Graphics g = Graphics.FromImage(image);
                g.DrawImage(copyImage, new Rectangle(image.Width-copyImage.Width, image.Height-copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width, copyImage.Height, GraphicsUnit.Pixel);
                g.Dispose();

                //儲存加浮水印過後的圖片,刪除原始圖片
                string newPath = Server.MapPath(".") + "/UploadFile/" + fileName + "_new" + extension;
                image.Save(newPath);
                image.Dispose();
                if(File.Exists(path))
                {
                    File.Delete(path);
                }

                Response.Redirect(newPath);
            }
        }