using System; 
using System.Collections; 
using System.Configuration; 
using System.Data; 
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.IO; 
//获取txt文件流 
namespace test 
{ 
 public partial class Text : System.Web.UI.Page 
 { 
  protected void Page_Load(object sender, EventArgs e) 
  { 
   Response.Write(GetInterIDList("asp.txt")); 
  } 
  //读取txt文件的内容 
  public string GetInterIDList(string strfile) 
  { 
   string strout; 
   strout = ""; 
   if (!File.Exists(System.Web.HttpContext.Current.Server.MapPath(strfile))) 
   { 
   } 
   else
   { 
    StreamReader sr = new StreamReader(System.Web.HttpContext.Current.Server.MapPath(strfile), System.Text.Encoding.Default); 
    String input = sr.ReadToEnd(); 
    sr.Close(); 
    strout = input; 
   } 
   return strout; 
  } 
 } 
}

string txtPath = Server.MapPath("~\\Public\\AttInfo\\") + "Test.txt"; 
StreamWriter sw = new StreamWriter(txtPath, false, System.Text.Encoding.Default); 
sw.WriteLine("Hello World"); 
sw.WriteLine(""); //输出空行 
sw.WriteLine("ASP.NET网络编程 - 编程素材网！"); 
sw.Close();

public void ProcessRequest(HttpContext context)
  {

   context.Response.Clear();
   context.Response.Buffer = true;
   //Server.UrlEncode 防止保存的文件名乱码
   context.Response.AddHeader("Content-Disposition", "attachment;filename=" + context.Server.UrlEncode("消费明细" + string.Format("{0:yyyyMMddHHmmss}", System.DateTime.Now) + ".txt")); 
   context.Response.ContentType = "text/plain"; 
   string message = "Hello World";
   //如果导出的文件要换行，用Environment.NewLine
   message += "Hello World" + Environment.NewLine;
   context.Response.Write(message);
   //停止页面的执行  
   context.Response.End(); 
  }