Post Back Does Not Work After Writing Files To Response?

What I have?I have a ASP.NET page which allows the user to download file a on a button click. User can select the file he wants from a list of available files (RadioButtonList) and clicks on download button to download it. (I should not provide link for each file that can be downloaded - this is the requirement).What I want?I want the user to download multiple files one by one by selecting the required radio button and clicking on the button.What problem am I facing?I can download the file for the first time properly. But, after downloading, if I select some other file and click on the button to download it, click event of the button does not post back and the second file will not be downloaded.I use the follwoing code on the button click event:

protected void btnDownload_Click(object sender, EventArgs e)
{
string viewXml = exporter.Export();
Response.Clear();
Response.AddHeader("Content-Disposition", "attachment; filename=views.cov");
Response.AddHeader("Content-Length", viewXml.Length.ToString());
Response.ContentType = "text/plain";
Response.Write(viewXml);
Response.End();
}