C# interview questions (Class)

 

Class Questions

1.What is the syntax to inherit from a class in C#? 
Place a colon and then the name of the base class.
Example: class MyNewClass : MyBaseClass 

2.Can you prevent your class from being inherited by another class? 
Yes. The keyword “sealed” will prevent the class from being inherited. 

3.Can you allow a class to be inherited, but prevent the method from being over-ridden?
Yes. Just leave the class public and make the method sealed. 

4.What’s an abstract class?
A class that cannot be instantiated. An abstract class is a class that must be inherited and has the methods overridden. An abstract class is essentially a blueprint for a class without any implementation. 

5.When do you absolutely have to declare a class as abstract?
1. When the class itself is inherited from an abstract class, but not all base abstract methods have been overridden. 
2. When at least one of the methods in the class is abstract. 

6.What is it an interface class?
Interfaces, like classes, define a set of properties, methods, and events. But unlike classes, interfaces do not provide the implementation. They are implemented by classes and defined as separate entities from classes. 

7.Why can’t you specify the accessibility modifier for methods inside the interface?
They all must be public and are therefore public by default. 
 
8.Can you inherit multiple interfaces?
Yes. .NET does support multiple interfaces. 

9.What happens if you inherit multiple interfaces and they have conflicting method names?
It’s up to you to implement the method inside your own class, so implementation is left entirely up to you. This might cause a problem on a higher-level scale if similarly named methods from different interfaces expect different data, but as far as compiler cares you’re okay. 

10. What’s the difference between an interface and abstract class?
In an interface class, all methods are abstract - there is no implementation. In an abstract class some methods can be concrete. In an interface class, no accessibility modifiers are allowed. An abstract class may have accessibility modifiers. 

11. What is the difference between a Struct and a Class?
Structs are value-type variables and are thus saved on the stack, additional overhead but faster retrieval. Another difference is that structs cannot inherit.