js+ajax实现获取文件大小的方法

<script language="Jscript">function chksize(){  var ticketType = "Oil";  var file1=document.getElementById("txtfile");  var v = file1.value;  file1.select();  var realpath = document.selection.createRange().text;  var input = "<Record><Type>TicketLoanResult</Type><TicketType>" + realpath + "</TicketType></Record>";  var objXmlHttp = new ActiveXObject("Microsoft.XMLHTTP");  objXmlHttp.Open("POST", "XMLHttpPost.aspx", false);  objXmlHttp.Send(input);  var returnXml = objXmlHttp.responseText;  if(returnXml!=null)  {   returnXml=parseInt(returnXml/1024/1024);  }  alert(returnXml);   return false; }</script>

public partial class XMLHttpPost : System.Web.UI.Page{ protected void Page_Load(object sender, EventArgs e) {  try  {   XmlDocument xmlDocumenet = new XmlDocument();   xmlDocumenet.Load(Request.InputStream);   string type = xmlDocumenet.SelectSingleNode("descendant::Type").InnerText;   string returnMessage = string.Empty;   switch (type.Trim())   {    case "TicketLoanResult":     returnMessage = GetTicketLoanResult(xmlDocumenet);     break;    default:     break;   }   Response.ContentType = "text/xml";   Response.Write(returnMessage);  }  catch (Exception exceptional)  {   //如果有返回信息（Xml格式）   string errorMessage = "<Error>" + exceptional.Message + "</Error>";   Response.ContentType = "text/xml";   Response.Write(errorMessage);  }  finally  {   Response.End();  } } private string GetTicketLoanResult(XmlDocument input) {  XmlNode item = input.SelectSingleNode("descendant::TicketType");  string ticketType = item.InnerText.Trim();  FileStream stream = new FileStream(ticketType,FileMode.Open);  return stream.Length.ToString(); }}