ASP.NET写入数据到TXT

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Text;
using System.IO;

namespace WebApplication1
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

        }

        protected void btnIP_Click(object sender, EventArgs e)
        {
            string txtip = txtIP.Text.Trim();
            string ip="";
            if (txtip != "")
            {
                if (txtip.Substring(txtip.Length - 1, 1) != ";")
                {
                    ip = txtip + ";";
                }
                else
                {
                    ip = txtip;
                }
                string path = Server.MapPath("IP.txt");
                if (!File.Exists(path))
                {
                    using (File.CreateText(path))
                    { }
                }

                StreamWriter sw = new StreamWriter(path, true);//true表示追加，false表示覆盖
                sw.Write(ip);

                sw.Close();
            }
            else
            { 
                //填写IP信息
            }
            
        }

        protected void btnRead_Click(object sender, EventArgs e)
        {
            string path = Server.MapPath("DenyIP.txt");
            string sameIP = "";
            FileStream fs = new FileStream(path, FileMode.Open);
            StreamReader sr = new StreamReader(fs, Encoding.Default);

            string result = null;
            while (!sr.EndOfStream)
            {
                result = sr.ReadLine();
            }

            if(result!="")
            {
                string[] arrayIP;
                if (result.Substring(result.Length - 1, 1) == ";")
                {
                     arrayIP = result.Substring(0,result.Length-1).Split(';');
                }
                else
                {
                    arrayIP = result.Split(';');
                }
                
                for (int i = 0; i < arrayIP.Length; i++)
                {
                    for (int j = 0; j < arrayIP.Length; j++)
                    {
                        if (i != j)
                        {
                            if (arrayIP[i] == arrayIP[j])
                            {
                                sameIP += arrayIP[i] + ";";
                            }
                        }                        
                    }
                }
            }


            txtIP.Text = sameIP;

            sr.Close();
            fs.Close();
        }
    }
}