How to return enum's values marked with custom attribute using C#

Question

I have an enum with some members marked by custom attribute like:

public enum VideoClipTypeEnum : int
{
    Exhibitions = 1,

    TV = 2,

    [ClipTypeDisplayAttribute(false)]
    Content = 3
}

My attribute is:

public class ClipTypeDisplayAttribute : DescriptionAttribute
    {
        #region Private Variables

        private bool _treatAsPublicType;

        #endregion

        #region Ctor

        public ClipTypeDisplayAttribute(bool treatAsPublicType)
        {
            _treatAsPublicType = treatAsPublicType;
        }

        #endregion

        #region Public Props

        public bool TreatAsPublicType
        {
            get
            {
                return _treatAsPublicType;
            }
            set
            {
                _treatAsPublicType = value;
            }
        }

        #endregion
    }

What is the best way of getting the values of members marked with my custom attribute into List?

Can you be more specific? There are no fields in your example - are you talking about enum members? Do you want to receive only enum members, that are marked with attributes? — evgenyl
– evgenyl, Commented Mar 21, 2013 at 6:35

p.s.w.g · Accepted Answer · 2013-03-21 07:02:21Z

2

Try this

var values = 
    from f in typeof(VideoClipTypeEnum).GetFields()
    let attr = f.GetCustomAttributes(typeof(ClipTypeDisplayAttribute))
                .Cast<ClipTypeDisplayAttribute>()
                .FirstOrDefault()
    where attr != null
    select f;

This will actually return the FieldInfo for the enum value. To get the raw value, try this.

var values = 
    ... // same as above
    select (VideoClipTypeEnum)f.GetValue(null);

If you also want to filter by some property of the attribute, you can do that too. Like this

var values = 
    ... // same as above
    where attr != null && attr.TreatAsPublicType
    ... // same as above

Note: This works because enum values (e.g. VideoClipTypeEnum.TV) are actually implemented as static, constant fields of the VideoClipTypeEnum internally.

To get a List<int> use this

var values = 
    (from f in typeof(VideoClipTypeEnum).GetFields()
     let attr = f.GetCustomAttributes(typeof(ClipTypeDisplayAttribute))
                 .Cast<ClipTypeDisplayAttribute>()
                 .FirstOrDefault()
     where attr != null
     select (int)f.GetValue(null))
    .ToList();

edited Mar 21, 2013 at 7:02

answered Mar 21, 2013 at 6:36

p.s.w.g

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3 Comments

Roman Over a year ago

Thanks! But what if I need to get the List<int> of values? I need that list to filter the videoClips in my repo.

Damien_The_Unbeliever Over a year ago

GetCustomAttributes<T>() is an extension that wraps up two of your steps and makes it more readable, IMO.

p.s.w.g Over a year ago

@Damien_The_Unbeliever seems like that's only available in 4.5, but good to know.

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