the code to connect dropdown list parameter with rdlc report

Question

I want the code that used to connect dropdown list parameter with RDLC report using reportviewer in (asp.net+c#) please

 

I want to connect dropdown list parameters with rdlc report, I need to filter according to 3 dropdown list parameters, I preview many youtube videos but they used codes(they do not display the code in attachment with their video)... for example the code in the minute 6.28 in this videohttps://www.youtube.com/watch?v=7PqwnreSdpg

 

can anyone help me please to get that code, or any another successful way can anyone help me???