FileUpLoad单击按钮，完成上传文件到服务器

//该方法是按钮单击事件，完成上传文件到服务器
private void btnUpload_Click(object sender, System.EventArgs e)
  {
    if(fileUpload1.PostedFile!=null && fileUpload1.PostedFile.FileName!="" &&    fileUpload1.PostedFile.ContentLength!=0)
    {
      if(fileUpload1.PostedFile.ContentLength > 5 * 1024 )
      {
    lblError.Text = "上传文件过大";
    lblError.Visible = true;
    return;
      }
      string sFileName = Path.GetExtension(fileUpload1.PostedFile.FileName).ToUpper();
      if(! (strFileName == ".BMP" || strFileName == ".GIF" || strFileName == ".JPG") )
      {
    lblError.Text = "文件格式不正确";
    lblError.Visible = true;
    return;
      }

      Random ran = new Random();
      string sNewImg = DateTime.Now.ToString(@"yyyyMMddHHmmss") + ran.Next(100,999) + Path.GetExtension(fileUpload1.PostedFile.FileName) ;
      string sPath = Server.MapPath( "~/Picture/" + sNewImg);
      if( !Directory.Exists(Path.GetDirectoryName(sPath) ) )
      {
        Directory.CreateDirectory(Path.GetDirectoryName(strPath));
      }
      fileUpload1.PostedFile.SaveAs(sPath);
    }       
  }