How to make Asynchronous(AJAX) File Upload using iframe?

I will answer my question , I think I found the solution. These are the steps that I followed to achieve the goal :

1. Make the attribute "target" of the form point to " iframe " .
2. Use a normal HTML request ( not Asynchronous/Ajax request ) to submit the form.
3. Because the target frame is iframe , the whole page will not be refreshed - just the iframe.
4. Once iframe onload event happens (capture that event using Javascript) then do what you want, e.g. You can send back a request to list recent uploaded file info.

The final code looks like this:

    <!-- Attach a file -->    <iframe id="uploadTrg" name="uploadTrg" height="0" width="0" frameborder="0" scrolling="yes"></iframe>    <form id="myForm" action="http://example.com/file-upload-service" method="post" enctype="multipart/form-data"  target="uploadTrg">        File: <input type="file" name="file">        <input type="submit" value="Submit" id="submitBtn"/>    </form>    <div id="ajaxResultTest"></div>

javascript :

$("iframe").load(function(){    // ok , now you know that the file is uploaded , you can do what you want , for example tell the user that the file is uploaded     alert("The file is uploaded");    // or you can has your own technique to display the uploaded file name + id ?     $.post('http://example.com/file-upload-service?do=getLastFile',null,function(attachment){       // add the last uploaded file , so the user can see the uploaded files       $("#ajaxResultTest").append("<h4>" + attachment.name + ":" + attachment.id "</h4>");    },'json');});

This example taken from BugKiller. complete working example which allows you to upload a logo and see it immediately in the html page, following which the upload value gets cleared:

html:

<form id="uploadForm" method="post" enctype="multipart/form-data"  target="uploadTrg">  <div id="fileUploadWrapper"><input type="file" name="file" id="fileUpload"></div>  <input type="submit" value="Upload" id="submitBtn"/></form><iframe id="uploadTrg" name="uploadTrg" height="0" width="0" frameborder="0" scrolling="no" style="display:none"></iframe><img id="imgLogo" style="border-width:0px;" />

javascript:

$(document).ready(function () {  var companynumber = '12345'; //get this from the database  var logoUploadUrl = 'UploadHandler.aspx?logoupload=true&companynumber=' + companynumber ;  $("#uploadForm").attr("action", logoUploadUrl);  $("#uploadTrg").load(function () {    //upload complete    //only way to reset contents of file upload control is to recreate it    $("#fileUploadWrapper").html('<input type="file" name="file" id="fileUpload">');    //reload the logo url, add ticks on the end so browser reloads it    var ticks = ((new Date().getTime() * 10000) + 621355968000000000);    var logoUrl = 'images/clients/' + companynumber + '/client.gif?' + ticks;    $("#imgLogo").attr('src', logoUrl);  });});

upload handler code behind (C#):

namespace MyWebApp {    public partial class UploadHandler : System.Web.UI.Page {        protected void Page_Load(object sender, EventArgs e) {          if (Request.Params["logoupload"] != null) {            string companynumber = Request.Params["companynumber"];            string savePath = Server.MapPath("\\images") + "\\clients\\" + companynumber + "\\client.gif";            if (File.Exists(savePath))                File.Delete(savePath);            //save the file to the server             Request.Files[0].SaveAs(savePath);            Response.Write("OK");            Response.Flush();            Response.End();          }       }}