How to enumerate an enum

Question

How can you enumerate an enum in C#?

E.g. the following code does not compile:

public enum Suit
{         


        

Answer 1

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

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

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...

Answer 2

You won't get Enum.GetValues() in Silverlight.

Original Blog Post by Einar Ingebrigtsen:

public class EnumHelper
{
    public static T[] GetValues<T>()
    {
        Type enumType = typeof(T);

        if (!enumType.IsEnum)
        {
            throw new ArgumentException("Type '" + enumType.Name + "' is not an enum");
        }

        List<T> values = new List<T>();

        var fields = from field in enumType.GetFields()
                     where field.IsLiteral
                     select field;

        foreach (FieldInfo field in fields)
        {
            object value = field.GetValue(enumType);
            values.Add((T)value);
        }

        return values.ToArray();
    }

    public static object[] GetValues(Type enumType)
    {
        if (!enumType.IsEnum)
        {
            throw new ArgumentException("Type '" + enumType.Name + "' is not an enum");
        }

        List<object> values = new List<object>();

        var fields = from field in enumType.GetFields()
                     where field.IsLiteral
                     select field;

        foreach (FieldInfo field in fields)
        {
            object value = field.GetValue(enumType);
            values.Add(value);
        }

        return values.ToArray();
    }
}

Answer 3

Three ways:

1. Enum.GetValues(type) // Since .NET 1.1, not in Silverlight or .NET Compact Framework
2. type.GetEnumValues() // Only on .NET 4 and above
3. type.GetFields().Where(x => x.IsLiteral).Select(x => x.GetValue(null)) // Works everywhere

I am not sure why GetEnumValues was introduced on type instances. 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 some 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 4

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 5

foreach (Suit suit in (Suit[]) Enum.GetValues(typeof(Suit)))
{
}

Note: The cast to (Suit[]) is not strictly necessary, but it does make the code 0.5 ns faster.