It is always public
In .NET interviews, when asked why you can’t specify access modifiers for items in an interface, you can explain it with the following points:
- Interface Nature: An interface in .NET serves as a contract defining a set of members (properties, methods, events) that implementing classes must provide. It’s a blueprint for classes to follow without prescribing how those members are implemented.
- Abstraction and Polymorphism: Interfaces promote abstraction and polymorphism by allowing different classes to implement them in various ways. They define what functionality is available but not how it’s implemented or accessed.
- Public by Default: Items in an interface are inherently public. Since the purpose of an interface is to define a contract for classes, all members of an interface are implicitly public and accessible to any class that implements the interface.
- Implementation Freedom: By not specifying access modifiers, interfaces allow implementing classes the freedom to decide the accessibility of members based on their specific requirements. This flexibility promotes encapsulation and helps in designing more maintainable and extensible code.
- Multiple Inheritance: In .NET, interfaces support multiple inheritance, allowing a class to implement multiple interfaces. Specifying access modifiers for interface members could lead to conflicts or unnecessary restrictions when a class implements multiple interfaces with different access modifiers.
In summary, interfaces in .NET are designed to define contracts without dictating implementation details, promoting flexibility, and supporting the principles of encapsulation and polymorphism. Thus, access modifiers are not specified for items in interfaces, as they are inherently public and accessible by implementing classes.