C# Language Specification

Interfaces

An interface defines a contract. A class or struct that implements an interface must adhere to its contract. An interface may inherit from multiple base interfaces, and a class or struct may implement multiple interfaces.

Interfaces can contain methods, properties, events, and indexers. The interface itself does not provide implementations for the members that it defines. The interface merely specifies the members that must be supplied by classes or structs that implement the interface.

1. Interface declarations

An interface-declaration is a type-declaration (§9.6) that declares a new interface type.

interface-declaration:
attributes_opt interface-modifiers_opt partial_opt interface
identifier variant-type-parameter-list_opt interface-base_opt
type-parameter-constraints-clauses_opt interface-body ;_opt

An interface-declaration consists of an optional set of attributes (§17), followed by an optional set of interface-modifiers (§13.1.1), followed by an optional partial modifier, followed by the keyword interface and an identifier that names the interface, followed by an optional variant-type-parameter-list specification (§13.1.3), followed by an optional interface-base specification (§13.1.4), followed by an optional type-parameter-constraints-clauses specification (§10.1.5), followed by an interface-body (§13.1.5), optionally followed by a semicolon.

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