How do I enumerate an enum in C#?

Question

How can you enumerate an enum in C#?

E.g. the following code does not compile:

public enum Suit 
{
    Spades,
    Hearts,
    Clubs,
    Diamonds
}

public void EnumerateAllSuitsDemoMethod() 
{
    foreach (Suit suit in Suit) 
    {
        DoSomething(suit);
    }
}

And gives the following compile-time error:

'Suit' is a 'type' but is used like a 'variable'

It fails on the Suit keyword, the second one.

Answer 1

A simple and generic way to convert an enum to something you can interact:

public static Dictionary<int, string> ToList<T>() where T : struct
{
   return ((IEnumerable<T>)Enum
       .GetValues(typeof(T)))
       .ToDictionary(
           item => Convert.ToInt32(item),
           item => item.ToString());
}

And then:

var enums = EnumHelper.ToList<MyEnum>();

Answer 2

This question appears in Chapter 10 of "C# Step by Step 2013"

The author uses a double for-loop to iterate through a pair of Enumerators (to create a full deck of cards):

class Pack
{
    public const int NumSuits = 4;
    public const int CardsPerSuit = 13;
    private PlayingCard[,] cardPack;

    public Pack()
    {
        this.cardPack = new PlayingCard[NumSuits, CardsPerSuit];
        for (Suit suit = Suit.Clubs; suit <= Suit.Spades; suit++)
        {
            for (Value value = Value.Two; value <= Value.Ace; value++)
            {
                cardPack[(int)suit, (int)value] = new PlayingCard(suit, value);
            }
        }
    }
}

In this case, Suit and Value are both enumerations:

enum Suit { Clubs, Diamonds, Hearts, Spades }
enum Value { Two, Three, Four, Five, Six, Seven, Eight, Nine, Ten, Jack, Queen, King, Ace}

and PlayingCard is a card object with a defined Suit and Value:

class PlayingCard
{
    private readonly Suit suit;
    private readonly Value value;

    public PlayingCard(Suit s, Value v)
    {
        this.suit = s;
        this.value = v;
    }
}

Answer 3

Add method public static IEnumerable<T> GetValues<T>() to your class, like

public static IEnumerable<T> GetValues<T>()
{
    return Enum.GetValues(typeof(T)).Cast<T>();
}

call and pass your enum, now you can iterate through it using foreach

 public static void EnumerateAllSuitsDemoMethod()
 {
     // custom method
     var foos = GetValues<Suit>(); 
     foreach (var foo in foos)
     {
         // Do something
     }
 }

Answer 4

Three ways:

1. Enum.GetValues(type) //since .NET 1.1, not in silverlight or compact framewok
2. type.GetEnumValues() //only on .NET 4 and above
3. type.GetFields().Where(x => x.IsLiteral).Select(x => x.GetValue(null)) //works everywhere

Not sure why was GetEnumValues introduced on type instance, it isn't very readable at all for me.

---

Having a helper class like Enum<T> is what is most readable and memorable for me:

public static class Enum<T> where T : struct, IComparable, IFormattable, IConvertible
{
    public static IEnumerable<T> GetValues()
    {
        return (T[])Enum.GetValues(typeof(T));
    }

    public static IEnumerable<string> GetNames()
    {
        return Enum.GetNames(typeof(T));
    }
}

Now you call:

Enum<Suit>.GetValues();
//or
Enum.GetValues(typeof(Suit)); //pretty consistent style

One can also use sort of caching if performance matters, but I don't expect this to be an issue at all

public static class Enum<T> where T : struct, IComparable, IFormattable, IConvertible
{
    //lazily loaded
    static T[] values;
    static string[] names;

    public static IEnumerable<T> GetValues()
    {
        return values ?? (values = (T[])Enum.GetValues(typeof(T)));
    }

    public static IEnumerable<string> GetNames()
    {
        return names ?? (names = Enum.GetNames(typeof(T)));
    }
}

Answer 5

There are two ways to iterate an Enum:

1. var values =  Enum.GetValues(typeof(myenum))
2. var values =  Enum.GetNames(typeof(myenum))

The first will give you values in form on a array of object, and the second will give you values in form of array of String.

Use it in foreach loop as below:

foreach(var value in values)
{
    //Do operations here
}

Answer 6

I do not hold the opinion this is better, or even good, just stating yet another solution.

If enum values range strictly from 0 to n - 1, a generic alternative:

public void EnumerateEnum<T>()
{
    int length = Enum.GetValues(typeof(T)).Length;
    for (var i = 0; i < length; i++)
    {
        var @enum = (T)(object)i;
    }
}

If enum values are contiguous and you can provide the first and last element of the enum, then:

public void EnumerateEnum()
{
    for (var i = Suit.Spade; i <= Suit.Diamond; i++)
    {
        var @enum = i;
    }
}

but that's not strictly enumerating, just looping. The second method is much faster than any other approach though...