C# page to get AD Details sharepoint

Im super new to sharepoint,

and was wondering how can i use C# coz there is page call Contact.aspx

and i would like to create a file Contact.cs just like how i did with the VS solution

but now it won't be able to debug right?

All i wanna do is to get the information from AD

and display it on the Contact.aspx that page

so guess i need to do the c# part.

I would be very appreciate if someone explains it in detail.

Thanks very much.