Q. How many ways can we maintain the state of a page?
Ans. 1. Client Side - 
            Query string, hidden variables, viewstate, cookies
        2. Server side
            application , cache, context, session, database

Q. What is the use of a multicast delegate?
Ans. A multicast delegate may be used to call more than one method.

Q. What is the use of a private constructor?
Ans. A private constructor may be used to prevent the creation of an instance for a class.

Q. What is the use of Singleton pattern?
Ans. A Singleton pattern .is used to make sure that only one instance of a class exists.