Limitation Alert: Only a single mime type can be sent or transmitted in each request/response cycle (although my knowledge on this topic may be up for debate).
Despite this limitation, there is a workaround available. By utilizing an iframe on the client side to "download the file", you can direct its src attribute to an ashx file that achieves the same result.
It is essential to establish a connection with the iframe's onload event so that your web page can monitor the completion of the download process and trigger any necessary logic accordingly.
Innovative Solution Update:
Upon further investigation, I have come to realize that my initial solution was somewhat lacking!
The challenge lies in the fact that iframes do not activate their onload event after downloading content. This event will only be triggered if the URL specified in the src attribute navigates to a different webpage. This behavior appears to be by design, as I learned... today!
So, what options are at our disposal now?!
Fortunately, it is feasible to transmit cookies to the client. Your web page must continuously check for the existence of this cookie on the client side. Once the presence of the cookie is detected, it signifies that the browser has successfully completed the download request. For detailed information on this workaround, refer to the following post:
Let me provide you with some code snippets related to the handler file (simulating a download) and the client side (utilizing an iframe for the task), which should offer you a clear understanding:
Webform1.aspx:
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApp.FileDownload.WebForm1" %>
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>iFrame Download</title>
<script type="text/javascript" src="Scripts/jquery-2.1.0.min.js"></script>
<script type="text/javascript" src="Scripts/jquery.cookie.js"></script>
<script type="text/javascript">
function foo() {
console.log('foo');
//execute post-download logic here
}
$(function () {
$('input').click(function () {
//ensure removal of
//cookie before download
$.removeCookie('downloaded');
var intrvl = setTimeout(function () { //this function checks for the cookie to track successful download
console.log('timer');
var value = $.cookie('downloaded');
if (value == 'true') {
clearTimeout(intrvl);
foo();
}
}, 1000);
//initiate the download
$('iframe').attr({
'src': 'download.ashx?id=' + $('#tbxRandomNumber').val()
});
});
});
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:TextBox ID="tbxRandomNumber" runat="server"></asp:TextBox>
<input type="button" value="Download" />
<iframe src="about:blank" style="display:none"></iframe>
<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Next Random Number" />
</div>
</form>
</body>
</html>
I have incorporated the jquery cookies plugin to assist in managing cookies effectively.
download.ashx:
using System;
using System.Web;
namespace WebApp.FileDownload
{
/// <summary>
/// Summary description for download
/// </summary>
public class download : IHttpHandler
{
public void ProcessRequest(HttpContext context)
{
context.Response.ContentType = "text/plain";
context.Response.SetCookie(new HttpCookie("downloaded","true")); //setting response cookie
string id = context.Request.QueryString["id"] == null ? "NULL" : context.Request.QueryString["id"];
string str = string.Format("Content with id {0} was generated at {1}", id, DateTime.Now.ToLongTimeString());
context.Response.AddHeader("Content-Disposition", "attachment; filename=test.txt");
context.Response.AddHeader("Content-Length", str.Length.ToString());
context.Response.Write(str);
context.Response.End();
}
public bool IsReusable
{
get
{
return false;
}
}
}
}