Interface Basics

Interface Basics

An interface declares a contract of members that implementing classes must provide, but supplies no implementation of its own (aside from default methods). It's declared with interface and conventionally named starting with I, like IShape. Interfaces define *what* a type can do, not *how* it does it.

Note: Interface members are implicitly public — you never write an access modifier on them.

Example: Interface Basics

using System;

interface IGreeter
{
    void Greet();
}

class EnglishGreeter : IGreeter
{
    public void Greet()
    {
        Console.WriteLine("Hello!");
    }
}

class Program
{
    static void Main(string[] args)
    {
        IGreeter g = new EnglishGreeter();
        g.Greet();
    }
}