What is the compiler used for .net

[Janyasree]

Hi Friends
I'm Janyasree new to .net.
these were the question asked in an interview can any one pls give the answer for these questions...

1.what is the compiler used for .net?
2.what does IIS do?
3.what are virtual distructors?
4.How can you provide security for webservices?
5.What is the difference between asp session and asp.net session?
6.Is webservices written in only c#?
7.What is a diffgram?
8.what is the difference between sqlconnection and oledb connection?

thank u