C# OOP MCQs

Question 1: Interface members have by default ______ accessibility.

Answer: A.

Interfaces are meant to be implemented in other classes, so by default, all the members have public accessibility. No other access modifiers can be applied to interface members. However, the interface itself can be public or defaults to internal.

Question 2: What to do if a class implements two interfaces which coincidently have one method with the same name and signature?

Answer: B

Implement at least one interface explicitly by using <InterfaceName>.<memberName> syntax. This way if two members have the same name, then C# compiler can know which member points to which interface. This also makes the code much readable, maintainable and clears confusion. Recommended practice is to always implement interface explicitly.

Question 3: Can one interface inherit from one or multiple interfaces in C#?

Answer: A

In C#, an interface or a class can inherit from one or more interfaces.

Question 4: Which of the following types can implement interfaces?

Answer: A, B

A class or a struct can implement one or more interfaces.

Question 5: Can we declare a protected member in an interface?

Answer: B

The interface cannot include any member other than the public. All the members are by default public. Also, you cannot use public keywords in an interface because by default all the members are public. The C# compiler will give an error if you have used the keyword public in the interface.

Start where you are. Use what you have. Do what you can. - Arthur Ashe