protected void CreateFile(string content,string str)
         {
             string path = Server.MapPath("~\\UploadFile\\" + str);
            if (!File.Exists(path))
            {
                FileStream fs=new FileStream(path,FileMode.Create,FileAccess.Write);
                StreamWriter sw=new StreamWriter(fs);
                sw.WriteLine(content);
                sw.Close();
               fs.Close();
            }
            else
            {

                FileStream fs = new FileStream(path, FileMode.Open, FileAccess.Write);
                StreamWriter sr = new StreamWriter(fs);
                sr.WriteLine(content);//开始写入值
                sr.Close();
                fs.Close();
            }
        }