FIS interview question

Oop concept->object,class,abstraction,polymorphism why we use abstract class? Write a program to show method overloading and overriding? write a program to show generics in c#? What is Attribute in c#? what are filters in mvc ? Types of filters and how to use them Normalization in sql Write a query to add the new column to the existing table which already was some data and new col should be NOT NULL