Composition

As we know, inheritance gives us an 'is-a' relationship. To make the understanding of composition easier, we can say that composition gives us a 'part-of' relationship. Composition is shown on a UML diagram as a filled diamond (see Figure 1).
If we were going to model a car, it would make sense to say that an engine is part-of a car. Within composition, the lifetime of the part (Engine) is managed by the whole (Car), in other words, when Car is destroyed, Engine is destroyed along with it. So how do we express this in C#?

public class Engine
{
 . . .
}

public class Car

{

    Engine e = new Engine();

    .......

}

As you can see in the example code above, Car manages the lifetime of Engine.