Fluent API is a nice thing, but I would go a different way in your case. Building a car draws me more towards the Builder pattern. That way you would hide a car being composed in a factory (not the factory method pattern) which accepts commands like you have now, but do not accept questions.
No manufacturer lets you know details about their new car unless it is completed and prepared to be announced. So you would have to send a command like GetMyCar()
for releasing a car first and it would perfectly make sense that if you call Mpg
on unfinished car you would get an exception. And it would still look good if you use that fluent pattern.
var builder = new CarBuilder();
// each building method returns `CarBuilder`
builder.BuildFrames(size).BuildChassis().AppendWheels(4)...
Ok, that's my opinion. However there are two more suggestions for your current situation you can choose from if you don't like the builder.
1) If user calls Mpg
before Weight
and Fuel
are set, thrown an exception with a message explaining the situation. Also add a proper documentation of the Mpg
method.
2) Make a constructor take all required parameters for other properties. This is, in my opinon, a better solution than the first one, because is states from the very start what you can expect.