ASP.NET实现文件下载

  private void download_Click(object sender, System.EventArgs e)
  {
   string filename = "file/test.csv";                                           //这里是虚拟路径
   string path = Server.MapPath(filename);
   System.IO.FileInfo file = new System.IO.FileInfo(path);

   if (file.Exists)
   {
    Response.Clear();
    Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);
    Response.AddHeader("Content-Length", file.Length.ToString());
    Response.ContentType = "application/octet-stream";
    Response.Filter.Close();
    Response.WriteFile(file.FullName);
    Response.End();
   }
   else
   {
    Response.Write("This file does not exist.");
   }
  }