Checking .Net frameworks is installed or not on local machine by C#

Question

I have a problem. I make an exe file by C#. Now I want to check local machine is installed .Net frameworks or not? If my local  already install it so my program run normal. And if my local not yet install .Net frame so my program have to download any .Net framework to my local. That is all my boss request. (As I know one program by .exe file can not check and download .Net framework file on local machine if it not yet install any .Net framework. If I make my program by setup file so I can control this.). Now I want to have one solution for that. Everyone! Can you help me about my boss request? Thanks!