Factory Methods

A factory method is a static method that builds a new object. There’s no formal support for this in C#, it’s just a common solution to a problem—a pattern, as popular idioms are often called in programming. We can get around the overload ambiguity problems by providing factory methods with different names. And the names can make it clear how we’re initializing the instance:

public static PolarPoint3D FromDistanceAndAngle(
  double distance, double angle)
{
    return new PolarPoint3D(distance, angle, 0);
}

public static PolarPoint3D FromAngleAndAltitude(
  double angle, double altitude)
{
    return new PolarPoint3D(0, angle, altitude);
}

We rather like this approach, although some people frown on it as insufficiently discoverable. (Most developers aren’t expecting to find static methods that act rather like constructors, and if nobody finds these methods, we’re wasting our time in providing them.) However, this pattern is used all over the .NET Framework libraries—DateTime, TimeSpan, and Color are popular types that all use this technique.