C# naming convention for enum and matching property

Question

Hi All,

I often find myself implementing a class maintaining some kind of own status property as an enum: I have a Status enum and ONE Status property of Status type. How should I solve this name conflict?

public class Car
{
  public enum Status
  {
    Off,
    Starting,
    Moving
  };

  Status status = Status.Off;

  public Status Status // <===== Won't compile =====
  {
    get { return status; }
    set { status = value; DoSomething(); }
  }
}

If the Status enum were common to different types, I'd put it outside the class and the problem would be solved. But Status applies to Car only hence it doesn't make sense to declare the enum outside the class.

What naming convention do you use in this case?

NB: This question was partially debated in comments of an answer of this question. Since it wasn't the main question, it didn't get much visibility.

EDIT: Filip Ekberg suggests an IMO excellent workaround for the specific case of 'Status'. Yet I'd be interesting to read about solutions where the name of the enum/property is different, as in Michael Prewecki's answer.

EDIT2 (May 2010): My favorite solution is to pluralize the enum type name, as suggested by Chris S. According to MS guidelines, this should be used for flag enums only. But I've come to like it more and more. I now use it for regular enums as well.

Answer 1

I usually prefix the enums, e.g. CarStatus. I suppose it all depends on team you're working with (if they have any rules/ processes for that sort of thing) and the objects usage. Just my 2 cents (:

Answer 2

The definition of "Off", "Starting" and "Moving" is what i would call a "State". And when you are implying that you are using a "State", it is your "Status". So!

public class Car
{
  public enum State
  {
    Off,
    Starting,
    Moving
  };

  State state = State.Off;

  public State Status
  {
    get { return state ; }
    set { state= value; DoSomething(); }
  }
}

If we take another example from the one stated where you'd like to use the word "Type" such in this case:

public class DataReader
{
    public enum Type
    {
        Sql,
        Oracle,
        OleDb
    }

    public Type Type { get; set; } // <===== Won't compile =====

}

You really need to see that there is a difference between enums and enums, right? But when creating a framework or talking about architecture you need to focus on the simillarities, ok lets find them:

When something is set to a State, it's defined as the "things" Status

Example: The Car's Status is in Running State, Stopped State, and so on.

What you want to acheive in the second example is somewhat this:

myDataReader.Type = DataReader.Database.OleDb

You might think that this says against what i've been preaching about to others, that you need to follow a standard. But, you are following a standard! The Sql-case is a specific case aswell and therefore need a somewhat specific solution.

However, the enum would be re-usable within your System.Data space, and that's what the patterns is all about.

Another case to look at with the "Type" is "Animal" where Type defines the Species.

public class Animal
    {
        public enum Type
        {
            Mammal,
            Reptile,
            JonSkeet
        }

        public Type Species{ get; set; }

    }

This is following a pattern, you don't specificly need to "know" the Object for this and you are not specifing "AnimalType" or "DataReaderType", you can re-use the enums in your namespace of choice.

Answer 3

I'd change the name of the property to something like "CurrentStatus". Quick an easy :)

Answer 4

I don't think there are many good solutions for this if you want to have the enum nested inside your class.

I actually prefer to have the enum separate then it doesn't present a problem, but I can see your point philosophically about wanting to nest it.

Answer 5

I think the real problem here is that the enum Status is encapsulated within your class, such that Car.Status is ambiguous to both the property Status and the enum Status

Better yet, put your enum outside of the class:

public enum Status
{
    Off,
    Starting,
    Moving
}

public class Car
{
    public Status Status
    { ... }
}

UPDATE

Due to the comments below, I'll explain my design above.

I'm one who doesn't believe that enums or classes or any other object should reside inside another class, unless it will be totally private within that class. Take the above example, for instance:

public class Car
{
    public enum Status
    {...}
    ...
    public Status CarStatus { get; set;}
}

While some commenters would argue that Status doesn't have any meaning outside the scope of the class Car, the fact that you are setting a public property means that there are other parts of the program that will use that enum:

public Car myCar = new Car();
myCar.CarStatus = Car.Status.Off;

And that to me is a code smell. If I'm going to look at that status outside of Car, I might as well define it outside as well.

As such, I will probably just rename it as:

public enum CarStatus
{...}

public class Car
{
    ...
    public CarStatus Status { get; set; }
}

However, if that enum will be used within and only within the car class, then I'm fine with declaring the enum there.

Answer 6

I'd like to offer the following example in support of the comment by Dan. C (made in response to Filip Ekberg's answer)

public class DataReader
{
    public enum Type
    {
        Sql,
        Oracle,
        OleDb
    }

    public Type Type { get; set; } // <===== Won't compile =====

}

Either the enum or the property could be called ReaderType but that's getting pretty close to prefixing things with MyObjectName...

So what would you name Type? Is there some sort of rule or train of thought you can follow to avoid naming your enumeration and a property on the class both the same?

If people want this to be a linked question then I will happily move it to another question.

Answer 7

I'll add my 1 euro to the discussion but it's probably not adding anything new.

The obvious solution is to move Status out of being a nested Enum. Most .NET enums (except possibly some in Windows.Forms namespace) aren't nested and it makes it annoying to use for the developer consuming your API, having to prefix the classname.

One thing that hasn't been mentioned is that noun phrase enums according to MSDN guidelines should be pluralized which you probably already know (Status is a noun so singular and that rule doesn't apply).

State (enum called States) is the vocative, "Status" is the nominative of a noun that the English like most of our language absorbed from Latin. Vocative is what you name a noun for its condition and nominative is the subject of the verb.

So in other words when the car is moving, that's the verb - moving is its status. But the car doesn't go off, its engine does. Nor does it start, the engine does (you probably picked an example here so this might be irrelevant).

public class Car
{
  VehicleState _vehicleState= VehicleState.Stationary;

  public VehicleState VehicleState 
  {
    get { return _vehicleState; }
    set { _vehicleState = value; DoSomething(); }
  }
}

public enum VehicleState
{
    Stationary, Idle, Moving
}

State is such a generalised noun wouldn't it be better to describe what state it is referring to? Like I did above

The type example also in my view doesn't refer to the reader type, but its database. I would prefer it if you were describing the reader's database product which isn't necessarily relevant to the type of reader (e.g. the type of reader might be forward only, cached and so on). So

reader.Database = Databases.Oracle;

In reality this never happens as they're implemented as drivers and an inheritance chain instead of using enums which is why the line above doesn't look natural.

Answer 8

I know my suggestion goes against the .NET Naming conventions, but I personally prefix enums with 'E' and enum flags with 'F' (similar to how we prefix Interfaces with 'I'). I really do not understand why this is not the convention. Enums/Flags are a special case like Interfaces that will never change their type. Not only does it make it clear what it is, it's very easy to type in intellisense since the prefix will filter most other types/variables/etc, and you won't have these naming clashes.

And that would also solve another problem where for examples in WPF they use static classes like enums (e.g. FontWeights) that have pre-defined instances of types but you would not know if you don't search for it. If they just prefixed them with 'E', all you would have to do is type on character to find these special static classes.