Is it possible to print rdlc report automatically?
If you can render it on a page you can use javascript window.print(), that prints current window. So as sinni800 said render report on separate page.
Something like this,
on page with other content add this button :
<a href="javascript:window.open('/print-content.html','_blank');">print report</a>
First parameter of open window is page with your report viewer, and in that page you can start print on load event, like this :
<body id="top" onload="window.print();">
rendered report here
</body>
But if you ask me better stick with your current solution.
You can save your report as PDF on disk, open it with Javscript and then print it, there is a example on Code Project for exactly your scenario as I understud you :
http://www.codeproject.com/Tips/376300/Custom-Print-functionality-for-Microsoft-Report-Vi