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c#.netloopsenumsenumeration
Ian Boyd
Ian Boyd

Reputation: 256571

How to enumerate an enum?

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 it 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.

Upvotes: 4409

Views: 1058314

Answers (30)

Sergey A Kryukov
Sergey A Kryukov

Reputation: 619

There is one essential flaw in other answers: some problems when your enumeration type has members with explicitly defined values, and if some values get identical values. Those identical values are sometimes used to provide synonyms. Besides, sometimes you need to exclude some auxiliary members for the traversal.

For a comprehensive solution with a number of extras please see my article Enumeration Types do not Enumerate! Working around .NET and Language Limitations. In other articles of my enumeration series referenced in this article, you can find some interesting applications of this approach.

Upvotes: 0

Tom Carr
Tom Carr

Reputation: 1439

I think you can use Enum.GetNames(Type enumType) method to retrieve an array of the names of the constants in a specified enumeration.

string[] suits = Enum.GetNames(typeof(Suit));

or the generic alternative:

string[] suits = Enum.GetNames<Suit>();

https://learn.microsoft.com/en-us/dotnet/api/system.enum.getnames

Upvotes: 73

Mostafa Bagheri
Mostafa Bagheri

Reputation: 403

Create an Extension for converting any enum to a list for binding to control by datasource

 public class KeyValueViewModel
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

            public static List<KeyValueViewModel> ConvertToList(this Enum en)
        {       
            return ((KeyValueViewModel[])Enum.GetValues(en.GetType())).Select(c => new KeyValueViewModel() { Id = c.Id, Name = c.ToString() }).ToList();
        }

Upvotes: 1

Arad
Arad

Reputation: 12685

New .NET 5+ Solution:

.NET 5 has introduced a new generic version for the GetValues method:

Suit[] suitValues = Enum.GetValues<Suit>();

Which is now by far the most convenient way of doing this.

Usage in a foreach loop:

foreach (Suit suit in Enum.GetValues<Suit>())
{

}

And if you just need the enum names as strings, you can use the GetNames method instead:

string[] suitNames = Enum.GetNames<Suit>();

Upvotes: 195

jop
jop

Reputation: 84043

Update: If you're using .NET 5 or newer, use this solution.

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.

Upvotes: 5316

nurchi
nurchi

Reputation: 800

For a future reader:

I do it this way:

public static class EnumHelpers
{
    public static Dictionary<TEnum, string> ToDictionary<TEnum>() where TEnum:Enum
    {
        var values = (TEnum[])Enum.GetValues(typeof(TEnum));

        return values
            .Select(v => (value: v, name: v.ToString()))
            .ToDictionary(vv=>vv.value, vn=>vn.name);
    }
}

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

Then, in some function, use it like this:

var Suits = EnumHelpers.ToDictionary<Suit>();

Suits is a Dictionary<Suit, string>.

There may need to be an additional check to get rid of the repeating values, maybe a call to Distinct() on values. Or the name could be used as the key, that way each name is unique even if a value repeats. Adjust as needed.

Upvotes: 3

marsh-wiggle
marsh-wiggle

Reputation: 2803

When you have a bit enum like this

enum DemoFlags
{
    DemoFlag = 1,
    OtherFlag = 2,
    TestFlag = 4,
    LastFlag = 8,
}

With this assignement

DemoFlags demoFlags = DemoFlags.DemoFlag | DemoFlags.TestFlag;

and need a result like this

"DemoFlag | TestFlag"

this method helps:

public static string ConvertToEnumString<T>(T enumToConvert, string separator = " | ") where T : Enum
{
    StringBuilder convertedEnums = new StringBuilder();

    foreach (T enumValue in Enum.GetValues(typeof(T)))
    {
        if (enumToConvert.HasFlag(enumValue)) convertedEnums.Append($"{ enumValue }{separator}");
    }

    if (convertedEnums.Length > 0) convertedEnums.Length -= separator.Length;

    return convertedEnums.ToString();
}

Upvotes: 5

Inam Abbas
Inam Abbas

Reputation: 486

I think its help you try it.

public class Program
{

    public static List<T> GetEnamList<T>()
    {
        var enums = Enum.GetValues(typeof(T)).Cast<T>().Select(v => v).ToList();
        return enums;
    }
    private void LoadEnumList()
    {
        List<DayofWeek> dayofweeks = GetEnamList<DayofWeek>();

        foreach (var item in dayofweeks)
        {
            dayofweeks.Add(item);
        }
    }
}

    public enum DayofWeek
    {
        Monday,
        Tuesday,
        Wensday,
        Thursday,
        Friday,
        Sturday,
        Sunday
    }

Upvotes: 3

R.Akhlaghi
R.Akhlaghi

Reputation: 760

For getting a list of int from an enum, use the following. It works!

List<int> listEnumValues = new List<int>();
YourEnumType[] myEnumMembers = (YourEnumType[])Enum.GetValues(typeof(YourEnumType));
foreach ( YourEnumType enumMember in myEnumMembers)
{
    listEnumValues.Add(enumMember.GetHashCode());
}

Upvotes: 7

MUT
MUT

Reputation: 606

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
     }
 }

Upvotes: 18

Kylo Ren
Kylo Ren

Reputation: 8803

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 an array of **object**s, and the second will give you values in form of an array of **String**s.

Use it in a foreach loop as below:

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

Upvotes: 37

anar khalilov
anar khalilov

Reputation: 17498

I know it is a bit messy, but if you are fan of one-liners, here is one:

((Suit[])Enum.GetValues(typeof(Suit))).ToList().ForEach(i => DoSomething(i));

Upvotes: 14

nawfal
nawfal

Reputation: 73153

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)));
    }
}

Upvotes: 41

Darkside
Darkside

Reputation: 1739

Just by combining the top answers, I threw together a very simple extension:

public static class EnumExtensions
{
    /// <summary>
    /// Gets all items for an enum value.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="value">The value.</param>
    /// <returns></returns>
    public static IEnumerable<T> GetAllItems<T>(this T value) where T : Enum
    {
        return (T[])Enum.GetValues(typeof (T));
    }
}

It is clean, simple, and, by @Jeppe-Stig-Nielsen's comment, fast.

Upvotes: 42

sircodesalot
sircodesalot

Reputation: 11439

Use Cast<T>:

var suits = Enum.GetValues(typeof(Suit)).Cast<Suit>();

There you go, IEnumerable<Suit>.

Upvotes: 149

nawfal
nawfal

Reputation: 73153

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...

Upvotes: 20

jhilden
jhilden

Reputation: 12419

Here is a working example of creating select options for a DDL:

var resman = ViewModelResources.TimeFrame.ResourceManager;

ViewBag.TimeFrames = from MapOverlayTimeFrames timeFrame
      in Enum.GetValues(typeof(MapOverlayTimeFrames))
      select new SelectListItem
      {
         Value = timeFrame.ToString(),
         Text = resman.GetString(timeFrame.ToString()) ?? timeFrame.ToString()
      };

Upvotes: 18

James
James

Reputation: 6103

I think this is more efficient than other suggestions because GetValues() is not called each time you have a loop. It is also more concise. And you get a compile-time error, not a runtime exception if Suit is not an enum.

EnumLoop<Suit>.ForEach((suit) => {
    DoSomethingWith(suit);
});

EnumLoop has this completely generic definition:

class EnumLoop<Key> where Key : struct, IConvertible {
    static readonly Key[] arr = (Key[])Enum.GetValues(typeof(Key));
    static internal void ForEach(Action<Key> act) {
        for (int i = 0; i < arr.Length; i++) {
            act(arr[i]);
        }
    }
}

Upvotes: 114

Aubrey Taylor
Aubrey Taylor

Reputation: 911

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();
    }
}

Upvotes: 91

Mallox
Mallox

Reputation: 1499

My solution works in .NET Compact Framework (3.5) and supports type checking at compile time:

public static List<T> GetEnumValues<T>() where T : new() {
    T valueType = new T();
    return typeof(T).GetFields()
        .Select(fieldInfo => (T)fieldInfo.GetValue(valueType))
        .Distinct()
        .ToList();
}

public static List<String> GetEnumNames<T>() {
    return typeof (T).GetFields()
        .Select(info => info.Name)
        .Distinct()
        .ToList();
}
  • If anyone knows how to get rid of the T valueType = new T(), I'd be happy to see a solution.

A call would look like this:

List<MyEnum> result = Utils.GetEnumValues<MyEnum>();

Upvotes: 71

bob
bob

Reputation: 6485

I made some extensions for easy enum usage. Maybe someone can use it...

public static class EnumExtensions
{
    /// <summary>
    /// Gets all items for an enum value.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="value">The value.</param>
    /// <returns></returns>
    public static IEnumerable<T> GetAllItems<T>(this Enum value)
    {
        foreach (object item in Enum.GetValues(typeof(T)))
        {
            yield return (T)item;
        }
    }

    /// <summary>
    /// Gets all items for an enum type.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="value">The value.</param>
    /// <returns></returns>
    public static IEnumerable<T> GetAllItems<T>() where T : struct
    {
        foreach (object item in Enum.GetValues(typeof(T)))
        {
            yield return (T)item;
        }
    }

    /// <summary>
    /// Gets all combined items from an enum value.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="value">The value.</param>
    /// <returns></returns>
    /// <example>
    /// Displays ValueA and ValueB.
    /// <code>
    /// EnumExample dummy = EnumExample.Combi;
    /// foreach (var item in dummy.GetAllSelectedItems<EnumExample>())
    /// {
    ///    Console.WriteLine(item);
    /// }
    /// </code>
    /// </example>
    public static IEnumerable<T> GetAllSelectedItems<T>(this Enum value)
    {
        int valueAsInt = Convert.ToInt32(value, CultureInfo.InvariantCulture);

        foreach (object item in Enum.GetValues(typeof(T)))
        {
            int itemAsInt = Convert.ToInt32(item, CultureInfo.InvariantCulture);

            if (itemAsInt == (valueAsInt & itemAsInt))
            {
                yield return (T)item;
            }
        }
    }

    /// <summary>
    /// Determines whether the enum value contains a specific value.
    /// </summary>
    /// <param name="value">The value.</param>
    /// <param name="request">The request.</param>
    /// <returns>
    ///     <c>true</c> if value contains the specified value; otherwise, <c>false</c>.
    /// </returns>
    /// <example>
    /// <code>
    /// EnumExample dummy = EnumExample.Combi;
    /// if (dummy.Contains<EnumExample>(EnumExample.ValueA))
    /// {
    ///     Console.WriteLine("dummy contains EnumExample.ValueA");
    /// }
    /// </code>
    /// </example>
    public static bool Contains<T>(this Enum value, T request)
    {
        int valueAsInt = Convert.ToInt32(value, CultureInfo.InvariantCulture);
        int requestAsInt = Convert.ToInt32(request, CultureInfo.InvariantCulture);

        if (requestAsInt == (valueAsInt & requestAsInt))
        {
            return true;
        }

        return false;
    }
}

The enum itself must be decorated with the FlagsAttribute:

[Flags]
public enum EnumExample
{
    ValueA = 1,
    ValueB = 2,
    ValueC = 4,
    ValueD = 8,
    Combi = ValueA | ValueB
}

Upvotes: 393

Er&#231;in Dedeoğlu
Er&#231;in Dedeoğlu

Reputation: 5383

LINQ Generic Way:

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

Usage:

        var enums = ToList<Enum>();

Upvotes: 1

rlv-dan
rlv-dan

Reputation: 1104

If you have:

enum Suit
{
   Spades,
   Hearts,
   Clubs,
   Diamonds
}

This:

foreach (var e in Enum.GetValues(typeof(Suit)))
{
    Console.WriteLine(e.ToString() + " = " + (int)e);
}

Will output:

Spades = 0
Hearts = 1
Clubs = 2
Diamonds = 3

Upvotes: 3

Liz
Liz

Reputation: 3033

Some versions of the .NET framework do not support Enum.GetValues. Here's a good workaround from Ideas 2.0: Enum.GetValues in Compact Framework:

public Enum[] GetValues(Enum enumeration)
{
    FieldInfo[] fields = enumeration.GetType().GetFields(BindingFlags.Static | BindingFlags.Public);
    Enum[] enumerations = new Enum[fields.Length];

    for (var i = 0; i < fields.Length; i++)
        enumerations[i] = (Enum) fields[i].GetValue(enumeration);

    return enumerations;
}

As with any code that involves reflection, you should take steps to ensure it runs only once and results are cached.

Upvotes: 205

Emily Chen
Emily Chen

Reputation: 166

enum types are called "enumeration types" not because they are containers that "enumerate" values (which they aren't), but because they are defined by enumerating the possible values for a variable of that type.

(Actually, that's a bit more complicated than that - enum types are considered to have an "underlying" integer type, which means each enum value corresponds to an integer value (this is typically implicit, but can be manually specified). C# was designed in a way so that you could stuff any integer of that type into the enum variable, even if it isn't a "named" value.)

The System.Enum.GetNames method can be used to retrieve an array of strings which are the names of the enum values, as the name suggests.

EDIT: Should have suggested the System.Enum.GetValues method instead. Oops.

Upvotes: 6

lmat - Reinstate Monica
lmat - Reinstate Monica

Reputation: 7768

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

I've heard vague rumours that this is terifically slow. Anyone know? – Orion Edwards Oct 15 '08 at 1:31 7

I think caching the array would speed it up considerably. It looks like you're getting a new array (through reflection) every time. Rather:

Array enums = Enum.GetValues(typeof(Suit));
foreach (Suit suitEnum in enums) 
{
    DoSomething(suitEnum);
}

That's at least a little faster, ja?

Upvotes: 59

Ross Gatih
Ross Gatih

Reputation: 679

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;
    }
}

Upvotes: 13

Termininja
Termininja

Reputation: 7036

Also you can bind to the public static members of the enum directly by using reflection:

typeof(Suit).GetMembers(BindingFlags.Public | BindingFlags.Static)
    .ToList().ForEach(x => DoSomething(x.Name));

Upvotes: 3

Joshua Drake
Joshua Drake

Reputation: 2746

public void PrintAllSuits()
{
    foreach(string suit in Enum.GetNames(typeof(Suits)))
    {
        Console.WriteLine(suit);
    }
}

Upvotes: 61

Gabriel
Gabriel

Reputation: 897

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>();

Upvotes: 13

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