protected void btn_addPicClick(object sender, EventArgs e)
        {
            txt_content.Value = txt_content.Value + "http://www.zushangpu.com" + uploadImage();
        }

        private string uploadImage()
        {
            try
            {
                if (fileUpload.FileBytes.Length > 10)
                {
                    string dirName = "/file";
                    string fileName = dirName + "/" + DateTime.Now.ToString("yyyyMMddHHmmss") + Path.GetExtension(fileUpload.FileName);
                    string dirPath = Server.MapPath(dirName);
                    string filePath = Server.MapPath(fileName);
                    if (!Directory.Exists(dirPath))
                        Directory.CreateDirectory(dirPath);
                    fileUpload.SaveAs(filePath);
                    return fileName;
                }
                else
                {
                    return null;
                }
            }
            catch
            {
                return null;
            }
        }