js判断上传文件大小 asp.net保存文件

<input type="file" name="file1" onchange="ShowSize(this.value)">
<script language="javascript">
<!--
function ShowSize(files)
{
var fso,f;
fso=new ActiveXObject("Scripting.FileSystemObject");
f=fso.GetFile(files);
if(f.size>1024*4){
alert(f.size+" Bytes");
}
}
//-->
</script>
</html>

<input type="text" size="4" value="10" name="fileSizeLimit" id="fileSizeLimit"/> K
<input type="file" name="file1" id="file1" size="40" onchange="changeSrc(this)"/>
<img src="about:blank" id="fileChecker" alt="test" height="18"/><script type="text/javascript">
var oFileChecker = document.getElementById("fileChecker");function changeSrc(filePicker)
{
oFileChecker.src = filePicker.value;
}oFileChecker.onreadystatechange = function ()
{
if (oFileChecker.readyState == "complete")
{
checkSize();
}
}function checkSize()
{
var limit = document.getElementById("fileSizeLimit").value * 1024; if (oFileChecker.fileSize > limit)
{
alert("too large");
}
else
{
alert("ok");
}
}
</script>

/// <summary>
/// 上传文件--返回保存的文件名
/// </summary>
private string UpFile()
{
   //FileUpload为Html的文件上传控件
   HttpPostedFile hpf=FileUpload.PostedFile;
   char[] sep={''};
   string[] AFileName=hpf.FileName.Split(sep);
   string GetFileName=AFileName[AFileName.Length-1];

   string ServerPath=Server.MapPath(@".UpFiles");
   if(!Directory.Exists(ServerPath))
   {
    Directory.CreateDirectory(ServerPath);
   }

   string RFileName=DateTime.Now.ToString("yyyyMMddHHmmss")+GetFileName;
   string path=ServerPath+RFileName;
   hpf.SaveAs(path);

   return RFileName;
}