失败的fileupload上传文件类型控制

 function openfile() {  try  {   var fd = new ActiveXObject("MSComDlg.CommonDialog");   fd.Filter = "上传文件 (*.doc,*.docx)|*.doc;*.docx";   fd.FilterIndex = 2;   // 必须设置MaxFileSize. 否则出错   fd.MaxFileSize = 128;   fd.ShowOpen();   document.getElementById("<%=txtFilepath.ClientID %>").value = fd.Filename;  }  catch (e)  {//   document.getElementById("<%=txtFilepath.ClientID %>").value = "";  } }