Include Header File With Extention .html In Asp

I want to make a web page in which I would include first header from header.html(it works fine),then sql connection subs from sql.asp,then variables from config.asp and so on.

when I write include for those asp files it doesn't seem to read them (no variables can be read)and when i try using server.execute,it shows me their content like in normal html files.I've tried to find a solution, but either I haven't looked long enough or it's not available.