文件上传与下载
protected void Button1_Click(object sender, EventArgs e)
  {
   
  }

  /// <summary>
  /// 上传文件 返回空为没有文件，返回0为格式错误！
  /// </summary>
  /// <returns></returns>
  private string UploadFile()
  {
  string directoryPath = "";
  string folderDate = "";
  string month = "";
  string day = "";
  string fileName = "";
  string fileNameLast = "";
  string saveAddr = "";
  if (DateTime.Now.Month < 10)
  { month = "0" + DateTime.Now.Month; }
  else
  { month = Convert.ToString(DateTime.Now.Month); }

  if (DateTime.Now.Day < 10)
  { day = "0" + DateTime.Now.Day; }
  else
  { day = Convert.ToString(DateTime.Now.Day); }
  folderDate = DateTime.Now.Year + "" + month + "" + day;

  if ((FileUpload1.PostedFile != null) && (FileUpload1.PostedFile.ContentLength > 0))
  {
  fileName = System.IO.Path.GetFileName(FileUpload1.PostedFile.FileName);

  fileNameLast = fileName.Substring(fileName.Length - 4, 4).ToLowerInvariant();
  if (!fileNameLast.Contains("zip") && !fileNameLast.Contains("txt") && !fileNameLast.Contains("rar") && !fileNameLast.Contains("doc"))
  {
  return "0";//文件格式错误！
  }
  Random r = new Random();
  fileName = Convert.ToString(r.Next(10000000, 99999999)) + fileNameLast;

  directoryPath = Server.MapPath("../file/" + folderDate + "/");
  if (Directory.Exists(directoryPath))//文件夹是否存在
  {
  saveAddr = Server.MapPath("../file/" + folderDate + "/") + fileName;
  FileUpload1.PostedFile.SaveAs(saveAddr);

  }
  else
  {
  Directory.CreateDirectory(directoryPath);
  saveAddr = Server.MapPath("../file/" + folderDate + "/") + fileName;
  FileUpload1.PostedFile.SaveAs(saveAddr);
  }
  }
  else
  {
  return "";
  }
  return "Images/" + folderDate + "/" + fileName;
  }


大家帮忙看下，那个上传按钮里应该怎么写？先谢谢了，很急，在线等，希望各位高手帮帮忙！

------解决方案--------------------
string rst=UploadFile();
就可以了啥

------解决方案--------------------
if (fileUpload.HasFile) 
{ 
string savePath = Server.MapPath("~/upload/"); 
if (!System.IO.Directory.Exists(savePath)) 
{ 
System.IO.Directory.CreateDirectory(savePath); 
} 
savePath = savePath + "\\" + fileUpload.FileName; 
fileUpload.SaveAs(savePath);//保存文件 
} 
path.GetExtention判断文件格式
下载response.writefile