将登陆人ip写入txt文件

public void WriteIpToTxt(string ip,string username)
        {
            string strfile;
            strfile = "asp.txt";

            string strout;
            strout = "";
            StreamReader sr = new StreamReader(System.Web.HttpContext.Current.Server.MapPath(strfile), System.Text.Encoding.Default);

            String input = sr.ReadToEnd();
            sr.Close();
            StreamWriter sw = new StreamWriter(Server.MapPath(strfile), false, System.Text.Encoding.Default);
            sw.Write(input + "登录人："+username+"\u0000");
            sw.Write("登录人IP：" + ip + "\u0000");
            sw.Write("登录时间："+DateTime.Now+"\r\n");
            sw.Close();
            strout = input;

        }