Why does streaming an image not work in modaldialog

Question

I'm adding some functionality to an existing 'popup' in an ASP.NET website. The popup is called by window.showmodaldialog because the website only needs IE support and well, ... it was just programmed that way many years ago.

Now when I try to stream an image ( show a save file dialog ), this code does not work. It does work on normal pages, and anything that isn't a modal dialog.

protected void ButtonExport_Click(object sender, EventArgs e)
{
        Response.Clear();
        Response.ContentType = "image/png";
        Response.AddHeader("content-disposition", "attachment;filename=print.png");
        MemoryStream img = DayPilotCalendar1.Export(ImageFormat.Png);
        img.WriteTo(Response.OutputStream);
        Response.End();
}

Is there any reason why this does not work? It's simply not displaying anything when I click the button, but it does go through the code.

Answer 1

Because window.showModalDialog opens a modal dialog which blocks the parent window. So the browser window is blocked and it is unable to show the Save dialog.

You can try to use window.showModelessDialog instead