Interface Interview Questions and Answers in CSharp
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1. What is an Interface in C#?
An interface in C# is a programming construct that defines a contract or a set of methods that a class must implement. It serves as a blueprint for the methods that implementing classes must provide. Interfaces don’t contain any method implementations; they specify the method signatures that participating classes must adhere to.
2. What are the different types of Inheritance Supported by C#?
C# supports two primary types of inheritance: single class inheritance and multiple interface inheritance. Single class inheritance allows a class to inherit from a single base class, while multiple interface inheritance enables a class to implement multiple interfaces, inheriting their method contracts.
3. Why do we need an interface in C#?
Interfaces are essential in C# to achieve multiple inheritance and ensure that classes adhere to a common contract. They help in promoting code standardization, allowing for the creation of classes with shared behaviors and capabilities, which leads to more maintainable and extensible code.
4. Can I use public access specifiers for interface methods in C#?
Interface methods in C# are implicitly public, so explicitly specifying ‘public’ access modifiers for these methods is redundant. All interface methods are public by default.
5. Can an Interface Implement an Abstract Class in C#?
No, interfaces cannot implement abstract classes. Interfaces define method contracts without any implementation, while abstract classes can provide partial method implementations. An abstract class can, however, implement an interface.
6. Can an Interface be Declared as Sealed in C#?
No, interfaces cannot be declared as sealed because they are meant to be implemented by classes. Sealing a class or method prevents further modifications, but interfaces are meant to be extended and implemented.
7. Is more than one Interface allowed to Implement a Class in C#?
Yes, a class in C# can implement multiple interfaces. This feature is crucial for achieving multiple inheritance and allowing a class to inherit behaviors from different sources.
8. Is it Necessary to Implement all Interface Methods in C#?
Yes, it is mandatory for a class implementing an interface to provide concrete implementations for all methods defined in the interface. Failing to do so will result in a compilation error.
9. How Interface is Different from a Class in C#?
An interface defines a contract specifying method signatures without any implementation. In contrast, a class can contain both method implementations and member variables, making it a more comprehensive unit of code.
10. What are the Similarities Between the Interface and Abstract Class in C#?
Both interfaces and abstract classes promote code reusability and abstraction. They allow you to define a set of methods or properties that derived classes must provide or implement.
11. What is the Difference Between Interface and Abstract Class in C#?
The key difference is that an interface is purely a contract with no implementation, while an abstract class can have a mix of abstract (unimplemented) and concrete (implemented) methods. You can inherit only one class, but implement multiple interfaces.
12. What are the Advantages of using Interface in C#?
The advantages of using interfaces in C# include promoting a clear separation of concerns, enabling flexible and maintainable code through multiple inheritance, and ensuring that classes adhere to shared contracts, leading to more robust and extensible software.