C#: Is there a way to classify enums?

C#: Is there a way to classify enums?

Given the following enum:

    public enum Position      {          Quarterback,          Runningback,          DefensiveEnd,          Linebacker      };  

Is it possible to classify the named constants, such that I could mark 'Quarterback' and 'Runningback' as offensive positions and 'DefensiveEnd' and 'Linebacker' as defensive positions?

Answer by Anton Gogolev for C#: Is there a way to classify enums?

You can use attributes:

public enum Position  {      [OffensivePosition]      Quarterback,      [OffensivePosition]      Runningback,      [DefensivePosition]      DefensiveEnd,      [DefensivePosition]      Linebacker  };  

And then check for IsDefined on an appropriate FieldInfo. Syntax is not very pretty, but you can throw in a couple of extension methods to make things more manageble:

public static bool IsOffensivePosition(PositionType pt)  {      return typeof(PositionType).GetField(Enum.GetName(typeof(PositionType), pt)).          IsDefined(typeof(OffensivePositionAttribute), false);  }  

Answer by cgreeno for C#: Is there a way to classify enums?

You could use Flags

[Flags]  public enum Position      {          Quarterback = 1,          Runningback = 2,          DefensiveEnd = 4,          Linebacker = 8,            OffensivePosition = Quarterback | Runningback,          DefensivePosition =  Linebacker | DefensiveEnd,         };        //strictly for example purposes      public bool isOffensive(Position pos)      {          return !((pos & OffensivePosition) == pos);      }  

Answer by Thomas Levesque for C#: Is there a way to classify enums?

You could use an attribute, like CategoryAttribute :

public enum Position  {      [Category("Offensive")]      Quarterback,      [Category("Offensive")]      Runningback,      [Category("Defensive")]      DefensiveEnd,      [Category("Defensive")]      Linebacker  };  

Answer by Matthew Whited for C#: Is there a way to classify enums?

You could use some form of flag bits. But that could lead to a mess. A better way may be to just create custom classes with the details you want and then use a Dictionary to lookup each position type;

public class PlayerPosition {      public PlayerPosition (string positionName, bool isDefensive ) {          this.Name = positionName;          this.IsDefensive = isDefensive ;      }      public string Name { get; private set; }      public bool IsDefensive { get; private set; }  }  

... as enum ...

[Flags]  public enum Positions {      Quarterback = 0x21,       Runningback = 0x22,       DefensiveEnd = 0x14,       Linebacker = 0x18,         Defensive = 0x10,      Offsensive = 0x20  }  

Answer by Jakub Šturc for C#: Is there a way to classify enums?

Maybe you can try to use typesefe enum pattern

class Position  {      public bool Offensive { get; private set; }      public bool Defensive { get; private set; }        private Position()      {          Offensive = false;          Defensive = false;      }        public static readonly Position Quarterback = new Position() { Offensive = true };      public static readonly Position Runningback = new Position() { Offensive = true };      public static readonly Position DefensiveEnd = new Position() { Defensive = true };      public static readonly Position Linebacker = new Position() { Defensive = true };  }  

Answer by dbemerlin for C#: Is there a way to classify enums?

Why not KISS:

class PlayerPosition {      public enum Position {          Quarterback,          Runningback,          DefensiveEnd,          Linebacker      }        public enum Type {          Offense,          Defense      }          public static Type GetTypeForPosition(Position position) {          switch (position) {              case Quarterback:              case Runningback:                  return Type.Offense;              case DefensiveEnd:              case Linebacker:                  return Type.Defense;            }      }  }  

Answer by LBushkin for C#: Is there a way to classify enums?

An underutilized (but perfectly valid) technique is to use a class which defines a set of constants. As a class, you can add additional properties that can describe other aspects of the enumerated value. Curiously, this is the way most enums are implemented in Java (which doesn't have a special keyword for them).

If you go this route, it's generally a good idea to make the class sealed and define a private constructor, so that only the class itself can define instances. Here's an example:

public static class Position   {      private PlayerPosition (string name, bool isDefensive ) {          this.Name = name          this.IsDefensive = isDefensive ;      }      // any properties you may need...      public string Name { get; private set; }      public bool IsDefensive { get; private set; }      public bool IsOffensive { get { return !IsDefensive; } }        // static instances that act like an enum      public static readonly Quarterback = new PlayerPosition( "Quarterback", false );      public static readonly Runningback = new PlayerPosition( "Runningback", false );      public static readonly Linebacker = new PlayerPosition( "Linebacker", true );      // etc...  }  

Using such an enum results in more elegant and simpler syntax than attributes:

if( PlayerPosition.Quarterback.IsDefensive )  {      // ...  }  

Answer by Jamie Ide for C#: Is there a way to classify enums?

You can declare the enums in a class:

public class Position  {      public enum Offensive { Quarterback = 1, RunningBack }      public enum Defensive { DefensiveEnd = 10, LineBacker }  }  

Note that the Defensive values start at 10 so that values don't overlap. You don't state why you want to do this, so this might not meet your needs.

Answer by Sergey Teplyakov for C#: Is there a way to classify enums?

public enum PositionType  {      Offensive,      Defensive,  }    public class PositionTypeAttribute : Attribute  {      public PositionTypeAttribute(PositionType positionType)      {          PositionType = positionType;      }      public PositionType PositionType { get; private set; }  }    public enum Position  {      [PositionType(PositionType.Offensive)]      Quarterback,      [PositionType(PositionType.Offensive)]      Runningback,      [PositionType(PositionType.Defensive)]      DefensiveEnd,      [PositionType(PositionType.Defensive)]      Linebacker  };    public static class PositionHelper  {      public static PositionType GetPositionType(this Position position)      {          var positionTypeAttr = (PositionTypeAttribute)typeof(Position).GetField(Enum.GetName(typeof(Position), position))              .GetCustomAttributes(typeof(PositionTypeAttribute), false)[0];          return positionTypeAttr.PositionType;        }  }      Position position1 = Position.Runningback;  Console.WriteLine(position1.GetPositionType()); //print: Offensive    Position position2 = Position.Linebacker;  Console.WriteLine(position2.GetPositionType()); //print: Defensive  

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