why we cannot use fields in interface c#

Question

Mukesh Kumar · Answer

Hi, Though many of the other answers are correct at the semantic level, I find it interesting to also approach these sorts of questions from the implementation details level. An interface can be thought of as a collection of slots , which contain methods . When a class implements an interface, the class is required to tell the runtime how to fill in all the required slots. When you say interface IFoo { void M (); } class Foo : IFoo { public void M () { ... } } the class says "when you create an instance of me, stuff a reference to Foo.M in the slot for IFoo.M. Then when you do a call: IFoo ifoo = new Foo (); ifoo . M (); the compiler generates code that says "ask the object what method is in the slot for IFoo.M, and call that method. If an interface is a collection of slots that contain methods, then some of those slots can also contain the get and set methods of a property, the get and set methods of an indexer, and the add and remove methods of an event. But a field is not a method . There's no "slot" associated with a field that you can then "fill in" with a reference to the field location. And therefore, interfaces can define methods, properties, indexers and events, but not fields. thanks

Priyaranjan K S · Answer

Hi Dev , Interface is like an agreement or better say Contract that asks the Class that implements the interface to define all the methods within the interface . Now methods within the interface can be defined inside the class by associating a logic for that class , but a field cannot be defined or implemented/assigned a value within the class . However value assignments can be done using Properties because they have a getter/setter method as below : interface IEmployee { string Name { get; set; } } public class Employee : IEmployee { private string name; public string Name // read-write instance property { get { return name; } set { name = value; } } } Thanks, Priyan If you found this useful Please mark this as Answer

Munesh Sharma · Answer

If an interface is a collection of slots that contain methods, then some of those slots can also contain the get and set methods of a property, the get and set methods of an indexer, and the add and remove methods of an event. But a field is not a method . There's no "slot" associated with a field that you can then "fill in" with a reference to the field location. And therefore, interfaces can define methods, properties, indexers and events, but not fields.

why we cannot use fields in interface c#

Answers (3)