How not to abort http response c#

Question

I need to run several methods after sending file to a user for a download. What happens is that after I send a file to a user, response is aborted and I can no longer do any

Answer 1

the user clicks on a download button on WebForm1.aspx to start downloading a file. then, after the file download is done (served by WebForm2.aspx), user is automatically redirected.

WebForm1.aspx

WebForm1.aspx.cs

protected void btnDL_Click(object sender, EventArgs e)
{
    var sent = Session["sent"];

    while (Session["sent"]==null)
    {// not sure if this is a bad idea or what but my cpu is NOT going nuts
    }

    StartNextMethod();
    Response.Redirect(URL);

}

WebForm2.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{
    Response.Clear();
    Response.AddHeader("content-disposition", "attachment;  filename=test.pdf");
    Response.ContentType = "application/pdf";
    byte[] a = System.Text.Encoding.UTF8.GetBytes("test");
    Response.BinaryWrite(a);
    Session["sent"] = true;
}

Global.asax.cs

protected void Session_Start(object sender, EventArgs e)
{
    Session["init"] = 0; // init and allocate session data storage
}

note: make sure don't use ashx (generic handler) to serve your download. for some reason, the session in ashx and aspx don't talk to each other, unless you implement this.