Loop through "selected" Enum values?

Question

I know how to loop through enum list of properties, but how would I loop through all "selected" enum properties? For example, if one did Prop1 | Prop2 against public enum Foo { Prop1; Prop2; Prop3 }, how would I achieve this?

This is what I have now:

var values = Enum.GetValues(typeof(FileStatus)).Cast<FileStatus>();
foreach (var value in values)
{
}

It loops through all enum properties, but I'd like to loop only the ones that were "selected".

Update: [Flags] attribute was set.

Update 2: The enum contains a large number of properties, I can't and won't type/hardcode a single property check, instead I want to dynamically loop through each of them and check if my enum instance Bar contains the looped item set.

@Hexxagonal: Doesn't matter. However, explicitly assigning values matters a whole lot. — Ben Voigt, Apr 24 '12 at 18:00
@Hexxagonal That's really more optional than anything. The enums may or may not each be powers of two. Whether or not the flags att. is set *should* matter, but really it doesn't. — Servy, Apr 24 '12 at 18:00
This question is being discussed on [Meta](http://meta.stackoverflow.com/questions/325659/closing-for-duplicate). — Glorfindel, Jun 07 '16 at 14:24

user7116 · Accepted Answer · 2012-04-24T18:11:28.360

28

How about the following:

FileStatus status = FileStatus.New|FileStatus.Amazing;

foreach (FileStatus x in Enum.GetValues(typeof(FileStatus)))
{
    if (status.HasFlag(x)) Console.WriteLine("{0} set", x);
}

Or in one fell LINQ swoop:

var flags = Enum.GetValues(typeof(FileStatus))
                .Cast<FileStatus>()
                .Where(s => status.HasFlag(s));

edited Apr 24 '12 at 18:11

answered Apr 24 '12 at 18:01

user7116

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+1, I agree, it only prints if the flag is set. – Tejs Apr 24 '12 at 18:08
Works wonderfully! `if` passes only when the looped enum property is set for the status! – Tower Apr 24 '12 at 18:15

score 4 · Answer 2 · answered Apr 24 '12 at 18:12

[Flags]
public enum Foo
{
    Prop1 = 1,
    Prop2 = 1 << 1,
    Prop3 = 1 << 2
}

public static class FooExtensions
{
    private static readonly Foo[] values = (Foo[])Enum.GetValues(typeof(Foo));

    public static IEnumerable<Foo> GetComponents(this Foo value)
    {
        return values.Where(v => (v & value) != 0);
    }
}

public static class Program
{
    public static void Main(string[] args)
    {
        var foo = Foo.Prop1 | Foo.Prop3;

        var components = foo.GetComponents().ToArray();
    }
}

score 3 · Answer 3 · answered Apr 24 '12 at 17:58

3

Assuming you have this set as a bitmask, then simply "and"-ing the values would determine which are selected.

 SomeEnum bitmask = value;

 if(bitmask & SomeEnum.Value1 > 0)
    // SomeEnum.Value1 was set

answered Apr 24 '12 at 17:58

Tejs

40,736
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3

`bitmask.HasFlag(SomeEnum.Value1)` is more readable and does the same thing – Daniel Mann Apr 24 '12 at 18:02
Good point! Still, it's nice to understand exactly what that is doing under the hood, for completeness sake. – Tejs Apr 24 '12 at 18:04

Servy · Answer 4 · 2012-04-24T18:11:18.103

1

FileStatus someValue = ...;
var selectedValues = new List<FileStatus>();
var allValues = Enum.GetValues(typeof(FileStatus)).Cast<FileStatus>();
foreach (var value in allValues )
{
  if(someValue & value != 0)//note bitwise AND, not logical AND.
  {
     selectedValues.Add(value);
     //this value is selected.  You can stick it in a List or do whatever with it.
  }
}

edited Apr 24 '12 at 18:11

answered Apr 24 '12 at 17:58

Servy

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score 0 · Answer 5 · answered Apr 24 '12 at 18:11

You would need to mark the enum with Flags attribute. To get the values you can use yourObject.EnumProperty.HasFlag method, for example:

class Program 
{
    [Flags]
    public enum Bar { Prop1, Prop2, Prop3 }

    public class Foo
    {
        public Bar SelectedBar { get; set; }
    }

    static void Main(string[] args)
    {
        var foo = new Foo();
        foo.SelectedBar = Bar.Prop1 | Bar.Prop2;

        foo.SelectedBar.HasFlag(Bar.Prop1); //true
        foo.SelectedBar.HasFlag(Bar.Prop2); //true
        foo.SelectedBar.HasFlag(Bar.Prop3); //false
    }
}

Loop through "selected" Enum values?

5 Answers5