C# Interfaces Questions with Answers | Page 3

C# Interfaces programming questions and answers are frequently asked in technical interviews and placement exams conducted by top companies like Tech Mahindra, Infosys, and Wipro. Interfaces in C# define a contract that classes and structs can implement, ensuring consistency and abstraction in code design. Understanding interfaces helps programmers achieve loose coupling and multiple inheritance in an object-oriented way. Practicing programming interview questions with answers based on interfaces improves one’s ability to design modular, scalable software systems. Candidates should explore interface inheritance, explicit implementation, and default methods introduced in modern C# to excel in interview coding rounds.

Questions on interfaces and abstraction in C. Complement with C++ polymorphism and encapsulation

Showing 10 of 38 questions

Per page:

Q21

Which of the following can implement an interface

A Class only
B Struct only
C Explanation: Both classes and structs can implement interfaces.
D Interface only

Answer: Option C

Explanation: Both classes and structs can implement interfaces.

Q22

What happens if a class does not implement all interface members

A Code compiles successfully
B Runtime error occurs
C Explanation: All interface members must be implemented, otherwise a compile-time error occurs.
D Interface methods are ignored

Answer: Option C

Explanation: All interface members must be implemented, otherwise a compile-time error occurs.

Q23

Which feature is mainly achieved using interfaces

A Encapsulation
B Explanation: Interfaces support polymorphism by allowing different implementations of the same contract.
C Data hiding
D Memory management

Answer: Option B

Explanation: Interfaces support polymorphism by allowing different implementations of the same contract.

Q24

Can an interface contain properties in C#

A No
B Yes, with implementation
C Explanation: Interfaces can declare properties but cannot implement them.
D Only static properties

Answer: Option C

Explanation: Interfaces can declare properties but cannot implement them.

Q25

Which version of C# introduced default interface methods

A C# 5.0
B C# 6.0
C C# 7.0
D Explanation: Default method implementations in interfaces were introduced in C# 8.0.

Answer: Option D

Explanation: Default method implementations in interfaces were introduced in C# 8.0.

Q26

What keyword is used to explicitly implement an interface member

A explicit
B override
C interface
D Explanation: Explicit interface implementation uses the interface name, not a keyword.

Answer: Option D

Explanation: Explicit interface implementation uses the interface name, not a keyword.

Q27

Why is explicit interface implementation used

A To improve performance
B Explanation: It is used to hide interface members from direct access through the class object.
C To create objects
D To avoid inheritance

Answer: Option B

Explanation: It is used to hide interface members from direct access through the class object.

Q28

Can an interface contain fields in C#

A Yes
B Explanation: Interfaces cannot contain fields.
C Only readonly fields
D Only static fields

Answer: Option B

Explanation: Interfaces cannot contain fields.

Q29

Which statement about interfaces is correct

A Interfaces can be instantiated
B Interfaces support constructors
C Explanation: Interfaces define a contract that implementing classes must follow.
D Interfaces store data

Answer: Option C

Explanation: Interfaces define a contract that implementing classes must follow.

Q30

How many interfaces can a class implement

A Only one
B Only two
C Explanation: A class can implement multiple interfaces.
D None

Answer: Option C

Explanation: A class can implement multiple interfaces.

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