Javascript 使用ajax与C#获取文件大小的实现

<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)
 {
  //如果有錯誤則返回錯誤信息（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();
 }
}