C# Language Idioms - Effective C# - page 58

public class Circle : Shape
{
private PointF center;
private float radius;
public Circle() :
this ( PointF .Empty, 0 )
{
}
public Circle( PointF c, float r)
{
center = c;
radius = r;
}
public override void Draw()
{
//...
}
static public implicit operator Ellipse ( Circle c)
{
return new Ellipse (c.center, c.center,
c.radius, c.radius);
}
}
Now that you've got the implicit conversion operator, you can use a Circle
anywhere an Ellipse is expected. Furthermore, the conversion happens
automatically:
public static double ComputeArea( Ellipse e)
{
// return the area of the ellipse.
return e.R1 * e.R2 * Math .PI;
}
// call it:
Circle c1 = new Circle ( new PointF ( 3.0f , 0 ), 5.0f );
ComputeArea(c1);