C#创建文件并往文件中写入信息

string filepath = Server.MapPath("~/Upfile") + "\\";   //要上传的文件夹的路径
            if (!Directory.Exists(filepath))  //不存在文件夹，创建
            {
                Directory.CreateDirectory(filepath);  //创建新的文件夹
            }
            Random myrdn = new Random(); //产生随机数
            //文件名称是用户名_时间随机数，放在filepath文件夹中
            string filename = filepath + "\\" + user + "_" + DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + DateTime.Now.Day.ToString() + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString() + DateTime.Now.Second.ToString() + myrdn.Next(10000).ToString() + ".txt";

            FileStream fs = File.Create(filename);  //创建文件
            fs.Close();
            StreamWriter sw = new StreamWriter(filename);  //创建写入流
            sw.Write("你好");

            sw.Flush();
            sw.Close();