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;

}