C#.NET — Is the following interface definition valid? interface IPerson { string FirstName { get; set; } string LastName { get; set; } void Print(); void Stock(); int Fun(); }

Introduction / Context:
Interfaces in C# define member signatures without implementation. This problem verifies whether properties and methods can be declared in an interface and whether bodies are required.

Given Data / Assumptions:

• IPerson declares two properties and three methods.
• No method or property accessor includes a body.

Concept / Approach:
In classic C#, interface members have signatures only. Implementing types must provide bodies. Properties in an interface are declared with get; and/or set; accessors — again, without bodies. Methods (void or returning values) are allowed and, similarly, have no bodies in the interface.

Step-by-Step Solution:

Verification / Alternative check:
Create a class Employee : IPerson and implement each member. The compiler will require bodies in the class.

Why Other Options Are Wrong:

• A/E are false because interfaces can declare properties and methods.
• C/D are false because bodies are not provided in interfaces (for this syllabus; default interface implementations came later and are not assumed here).

Common Pitfalls:
Trying to put code into interface accessors or methods; implementation belongs in classes/structs that implement the interface.

Final Answer:
This is a perfectly workable interface.