Virtual Static Void

Switching on Enums

Having read Jared Parsons blog entry on Switching on Types, I was inspired to follow on with a class that switches on enumerated values. This is achievable using a regular switch, but this approach seems more elegant.

The expected usage as follows:

  // given enumeration
  public enum HoldingField
  {
    Holding,
    BookValue,
    MarketValue,
    EffectiveExposure,
  }

  ...

  // code to extract result from respective property of "h"
  decimal result = 0m;
  EnumSwitch.Do
    (
      HoldingField,
      EnumSwitch.Case(HoldingField.Holding, ()=> result = h.Holding),
      EnumSwitch.Case(HoldingField.BookValue, ()=> result = h.BookValue),
      EnumSwitch.Case(HoldingField.MarketValue, ()=> result = h.MarketValue),
      EnumSwitch.Case(HoldingField.EffectiveExposure, ()=> result = h.EffectiveExposure)
    );

Here is the code for the EnumSwitch class:

  public static class EnumSwitch
  {
    public class CaseInfo
    {
      public bool IsDefault { get; set; }
      public Enum Target { get; set; }
      public Action Action { get; set; }
    }
    public static void Do(Enum source, params CaseInfo[] cases)
    {
      foreach (var entry in cases)
      {
        if (entry.IsDefault || source == entry.Target)
        {
          entry.Action(source);
          break;
        }
      }
    }
    public static CaseInfo Case(Enum value, Action action)
    {
      return new CaseInfo()
      {
        Action = x => action(),
        Target = value
      };
    }
    public static CaseInfo Default(Action action)
    {
      return new CaseInfo()
      {
        Action = x => action(),
        IsDefault = true
      };
    }
  }