How to define an enum has multiple value that is another enum

Question

I have two enum like below. But I don't know I can define enum like below. I tried. It seems to work. My first question. Can I define an enum like below ?

[Flags]
public enum SState : int
{
    ManuelPassive = 2501601,
    AutoPassive = 2501602,
    ManuelActive = 2501610,
    AutoActive = 2501611,
}

public enum SType : int
{
    All,
    Active = SState .AutoActive | SState .ManuelActive,
    Passive = SState .AutoPassive | SState .ManuelPassive,
}

My second question : If I can define this enum, How can I convert a SType value to SState list ?

public statis List<SState> ToList(this SType stype)
{
    // What should I do here ? 
}

Example Calling :

var list = SType.Active.ToList();

I want this list to be like below :

var list = new List<SState>{ SState.AutoActive, SState.ManuelActive };

Answer 1

The first question is fine - it will compile without problems as long as you don't have a circular definition.

Your second question is more interesting - one solution is to use the Type-Safe Enumeration pattern popularised by Java.

This pattern allows you to add new behaviours to your enums (something a language like Swift supports out of the box, but C# and Java sadly don't). In the below example I have given your enum a Value and a List property, as requested.

void Main()
{
    Console.WriteLine(SType.Active.Value);
    Console.WriteLine(SType.Active.List);
}

[Flags]
public enum SState : int
{
    ManuelPassive = 2501601,
    AutoPassive = 2501602,
    ManuelActive = 2501610,
    AutoActive = 2501611,
}

public sealed class SType
{
    public static readonly SType Active = new SType(new List<SState>() { SState.AutoActive, SState.ManuelActive });

    public static readonly SType Passive = new SType(new List<SState>() { SState.AutoPassive, SState.ManuelPassive });

    private SType (List<SState> values)
    {
        this.Value = (int)values.Aggregate((current, next) => current | next);
        this.List = values;
    }

    public int Value { get; private set; }

    public List<SState> List { get; private set; }
}