how can i use switch statement on type-safe enum pattern

Question

I found a goodlooking example about implementation enums in a different way. That is called type-safe enum pattern i think. I started using it but i realized th

Answer 1

The type-safe enum pattern is interesting because you can add behavior to individual enum members (which are instances). So, if the behavior you want to switch-on could be part of the class, just use polymorphism. Note that you might need to create subclasses for each member that overrides the behavior:

public class MyState {

  public static readonly MyState Passed = new MyStatePassed();
  public static readonly MyState Failed = new MyStateFailed();

  public virtual void SomeLogic() {
    // default logic, or make it abstract
  }

  class MyStatePassed : MyState {
    public MyStatePassed() : base(1, "OK") { }
  }
  class MyStateFailed : MyState {
    public MyStateFailed() : base(2, "Error") { }
    public override void SomeLogic() { 
      // Error specific logic!
    }
  }

  ...
}

Usage:

MyState state = ...
state.someLogic();

Now, if the logic clearly doesn't belong and you really want to switch, my advice is to create a sibling enum:

public enum MyStateValue { 
  Passed = 1, Failed = 2
}
public sealed class MyState {
  public static readonly MyState Passed = new MyState(MyStateValue.Passed, "OK");
  public static readonly MyState Failed = new MyState(MyStateValue.Failed, "Error");

  public MyStateValue Value { get; private set; }

  private MyState(MyStateValue value, string name) {
    ...
  }
}

And switch on that:

switch (state.Value) {
  case MyStateValue.Passed: ...
  case MyStateValue.Failed: ...
}

In this case, if the type-safe enum class doesn't have any behavior, there's not much reason for it to exist in place of the enum itself. But of course, you can have logic and a sibling enum at the same time.