Strategy pattern is one of the 23 design patterns 
available. The basic concept of strategy pattern is object 
composition at runtime. When you have multiple classes each 
having similar behaviour but the behaviour could change 
based on an external factor or the object itself. For 
example take a car, a car can have an engine, a steering 
wheel, 4 tyres e.t.c but a remote control car will not have 
an engine but will have the other characteristics of a 
normal car. For this case let us have the following code:
Interface HasEngine
{
void Engine();
}
Interface Tyres
{
void 4Tyres();
}

class Hummer:HasEngine,Tyres
{
override void Engine()
{
Console.WriteLine("Has Engine");
}
override void 4Tyres()
{
Console.WriteLine("Has 4 tyres");
}
}
class RemoteCar:HasEngine,Tyres
{
override void Engine()
{
Console.WriteLine("Has no Engine");
}
override void 4Tyres()
{
Console.WriteLine("Has 4 tyres");
}
}
class Car
{
HasEngine HE;
Tyres T;
setEngine(HasEngine obj)
{
HE=obj;
}
setTyres(Tyres obj)
{
T=obj;
} 
}
class MainClass:Car
{
HasEngine he;
Tyres  tyr;
setInstance()
{
he = new Hummer();
tyr = new Hummer();
}
public static void Main()
{
MainClass mc = new Car();
mc.setInstance();
mc.setEngine(he);
mc.setTyres(tyr);
}
}