Use interface keyword to define an interface : interface « Class « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. Class
3. interface

using System;

interface Interface1
{
   void PrintOut(string s);
}

class MyClass : Interface1
{
   public void PrintOut(string s)
   {
      Console.WriteLine("Calling through: {0}", s);
   }
}

class MainClass
{
   static void Main()
   {
      MyClass mc = new MyClass();
      mc.PrintOut("object.");
   }
}

Calling through: object.