HTML File
--------------------------------
<script language="javascript">
var url = "ajax/ajaxFile.aspx";
var binary;
var filename;
var mytext;

function upload() {
     filename = document.getElementById('myfile').value;
     mytext = document.getElementById('mytext').value;
     document.getElementById('ajaxbutton').disabled = true;

     // request local file read permission
     try {
         netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
     } catch (e) {
         alert("Permission to read file was denied.");
     }
       
     // open the local file
     var file = Components.classes["@mozilla.org/file/local;1"]
         .createInstance(Components.interfaces.nsILocalFile);
     file.initWithPath( filename );          
     stream = Components.classes["@mozilla.org/network/file-input-stream;1"]
         .createInstance(Components.interfaces.nsIFileInputStream);
     stream.init(file,    0x01, 00004, null);
     var bstream =  Components.classes["@mozilla.org/network/buffered-input-stream;1"]
         .getService();
     bstream.QueryInterface(Components.interfaces.nsIBufferedInputStream);
     bstream.init(stream, 1000);
     bstream.QueryInterface(Components.interfaces.nsIInputStream);
     binary = Components.classes["@mozilla.org/binaryinputstream;1"]
         .createInstance(Components.interfaces.nsIBinaryInputStream);
     binary.setInputStream (stream);

     // start AJAX file upload in 1 second
     window.setTimeout("ajax_upload()", 1000);
}

function ajax_upload() {
     // request more permissions
     try {
         netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
     } catch (e) {
         alert("Permission to read file was denied.");
     }

     http_request = false;
     http_request = new XMLHttpRequest();
     if (!http_request) {
         alert('Cannot create XMLHTTP instance');
         return false;
     }

     // prepare the MIME POST data
     var boundaryString = 'capitano';
     var boundary = '--' + boundaryString;
     var requestbody = boundary + '\n'
     + 'Content-Disposition: form-data; name="mytext"' + '\n'
     + '\n'
     + mytext + '\n'
     + '\n'
     + boundary + '\n'
     + 'Content-Disposition: form-data; name="myfile"; filename="'
         + filename + '"' + '\n'
     + 'Content-Type: application/octet-stream' + '\n'
     + '\n'
     + escape(binary.readBytes(binary.available()))
     + '\n'
     + boundary;

     document.getElementById('sizespan').innerHTML =
         "requestbody.length=" + requestbody.length;
       
     // do the AJAX request
     http_request.onreadystatechange = requestdone;
     http_request.open('POST', url, true);
     http_request.setRequestHeader("Content-type", "multipart/form-data; \
         boundary=\"" + boundaryString + "\"");
     http_request.setRequestHeader("Connection", "close");
     http_request.setRequestHeader("Content-length", requestbody.length);
     http_request.send(requestbody);

}

function requestdone() {
     if (http_request.readyState == 4) {
         if (http_request.status == 200) {
             result = http_request.responseText;
             document.getElementById('myspan').innerHTML = result;              
         } else {
             alert('There was a problem with the request.');
         }
         document.getElementById('ajaxbutton').disabled = false;
     }
}

</script>

<form>
Text: <input type="text" id="mytext" name="mytext" size="40">
<br>
File: <input type="file" id="myfile" name="datafile" size="40"><br>
<input type="button" id="ajaxbutton" value="AJAX IT" onclick="upload();">
</form>

<div id="sizespan"></div>
<hr>
<div id="myspan"></div>
--------------------------------------------------------------
asp.net File
protected void Page_Load(object sender, EventArgs e)
     {
         if (Request.Files.Count > 0)
         {
             try
             {
                 for (int i = 0; i < Request.Files.Count; i++)
                 {

                     int values = Request.Files.FileName.LastIndexOf('\\');
                     string filename = Request.Files.FileName.Substring(values + 1);
                     String strSavePath = Server.MapPath(ConfigurationManager.AppSettings["NewsImage"]) +"\\"+ filename;
                     Response.Write(strSavePath);
                     Request.Files.SaveAs(strSavePath);
                 }
             }
             catch(Exception objEx)
             {
                 Response.Write(objEx.Message);
             }
         }
         else
         {
             Response.Write(" khong co file");
         }
     }