How to read the Value for an EnumMember attribute

Question

public enum Status
    {

        Pending,
        [EnumMember(Value = "In Progress")]
        InProgress,
        Failed,
        Success
    }

string dbValue = "In Progress";
if (dbValue == ValueOf(Status.InProgress)){
//do some thing
}

How do I read the Value of Status.InProgress so I get back "in Progress"?

Harrier

Answer 1

This is an extension method that works with C# 8 and nullable reference types:

public static string? GetEnumMemberValue<T>(this T value)
    where T : Enum
{
    return typeof(T)
        .GetTypeInfo()
        .DeclaredMembers
        .SingleOrDefault(x => x.Name == value.ToString())
        ?.GetCustomAttribute<EnumMemberAttribute>(false)
        ?.Value;
}

Original Answer:

I've adapted this for .NET Core. Here it is:

public static String GetEnumMemberValue<T>(T value)
    where T : struct, IConvertible
{
    return typeof(T)
        .GetTypeInfo()
        .DeclaredMembers
        .SingleOrDefault(x => x.Name == value.ToString())
        ?.GetCustomAttribute<EnumMemberAttribute>(false)
        ?.Value;
}

Confluent

.SingleOrDefault(x => x.Name == value.ToString()) <-- Methinks that can be significantly optimized... – Gratulate

Answer 2

Something like this:

public string GetEnumMemberAttrValue(Type enumType, object enumVal)
{
      var memInfo = enumType.GetMember(enumVal.ToString());
      var attr = memInfo[0].GetCustomAttributes(false).OfType<EnumMemberAttribute>().FirstOrDefault();
      if(attr != null)
      {
          return attr.Value;
      }

      return null;
}

Usage:

var enumType = typeof(Status);
var enumVal = Status.InProgress;
var str = GetEnumMemberAttrValue(enumType,enumVal);

Exploratory

Answer 3

Borrowing from Amir's answer, a slightly nicer version is possible using generics as follows:

public string GetEnumMemberAttrValue<T>(T enumVal)
{
    var enumType = typeof(T);
    var memInfo = enumType.GetMember(enumVal.ToString());
    var attr = memInfo.FirstOrDefault()?.GetCustomAttributes(false).OfType<EnumMemberAttribute>().FirstOrDefault();
    if (attr != null)
    {
        return attr.Value;
    }

    return null;
}

Usage as follows:

var enumVal = Status.InProgress;
var str = GetEnumMemberAttrValue(enumVal);

As far as I'm aware T can't be constrained to enum's using a where clause. I would be happy to be corrected though.

Pugnacious

You can as of c# 7.3: learn.microsoft.com/en-us/dotnet/csharp/whats-new/… – Oubre

Answer 4

Wrapped it in an extension to make it feel more natural:

public static class Extension
{
    public static string ToEnumMemberAttrValue(this Enum @enum)
    {
        var attr = 
            @enum.GetType().GetMember(@enum.ToString()).FirstOrDefault()?.
                GetCustomAttributes(false).OfType<EnumMemberAttribute>().
                FirstOrDefault();
        if (attr == null)
            return @enum.ToString();
        return attr.Value;
    }
}

Usage:

string dbValue = "In Progress";
if (dbValue == Status.ToEnumMemberAttrValue())){
    //do some thing
}

Fic

Answer 5

If you have Newtonsoft in your project, that is what you should do:

to the Enum, you should add the attribute [JsonConverter(typeof(StringEnumConverter))]

and now you can call the JsonConvertor to serialize your value as the member string value.

in your example, it should be like that

[JsonConverter(typeof(StringEnumConverter))]
public enum Status
{

    Pending,
    [EnumMember(Value = "In Progress")]
    InProgress,
    Failed,
    Success
}

string dbValue = "In Progress";
if (dbValue == JsonConvert.SerializeObject(Status.InProgress)){
//do some thing
}

Note as mentioned by @Dinesh in the comment that the string is JSON therefor return with quatos so you can workaround that to get a clean string with strin.Replace method as:

dbValue == JsonConvert.SerializeObject(Status.InProgress).Replace("\"","");

Derogatory

The JsonConvert SerializeObject returned the enum string with double quotes, do you have any solution for this issue? – Loophole

@DineshPhalwadiya yes, you are right. actualy I used it with string.Replace method like so: JsonConvert.SerializeObject(whatever).Replace("\"","") – Derogatory

Thanks for the response @Derogatory , I used StringEnumConverter & EnumMember to work it for me – Loophole

Answer 6

A problem with all of the approaches post so far is that they use GetCustomAttribute<EnumMemberAttribute> for every lookup, which is somewhat expensive.

Given that attributes loaded from reflection are immutable it makes sense to cache the GetCustomAttribute<> result in-memory for each enum type (TEnum) being looked-up.

A static class<T> that's generic over T with a static initializer effectively acts as a singleton for every T, which can be used to own an ImmutableDictionary to efficiently and lazily cache the enum member attribute data:

Because the code below is generic over TEnum : struct, Enum it means there is also no boxing of enum values and it supports enums of varying underlying-type (e.g. enum Foo : int, enum Bar : long, etc):

public static class EnumMemberNames
{
    public static String? GetNameOrNull<TEnum>( TEnum value )
        where TEnum : struct, Enum
    {
        return EnumAttribCache<TEnum>.cachedNames.TryGetValue( value, out String? text ) ? text : null;
    }

    public static String GetName<TEnum>( TEnum value )
        where TEnum : struct, Enum
    {
        return GetNameOrNull( value ) ?? value.ToString();
    }

    private static class EnumAttribCache<TEnum>
        where TEnum : struct, Enum
    {
        public static readonly ImmutableDictionary<TEnum,String> cachedNames = LoadNames();

        private static ImmutableDictionary<TEnum,String> LoadNames()
        {
            return typeof(TEnum)
                .GetTypeInfo()
                .DeclaredFields
                .Where( f => f.IsStatic && f.IsPublic && f.FieldType == typeof(TEnum) )
                .Select( f => ( field: f, attrib: f.GetCustomAttribute<EnumMemberAttribute>() ) )
                .Where( t => ( t.attrib?.IsValueSetExplicitly ?? false ) && !String.IsNullOrEmpty( t.attrib.Value ) )
                .ToDictionary(
                    keySelector    : t => (TEnum)t.field.GetValue( obj: null )!,
                    elementSelector: t => t.attrib!.Value!
                )
                .ToImmutableDictionary();
        }
    }
}

Used like so:

enum Foo
{
    [EnumMemberAttribute( Value = "first" )]
    A = 1,

    [EnumMemberAttribute( Value = "second" )]
    B = 2,

    Unnamed = 4
}

public static void Main()
{
    Console.WriteLine( EnumMemberNames.GetNameOrNull( Foo.A ) ); // "first"
    Console.WriteLine( EnumMemberNames.GetNameOrNull( Foo.B ) ); // "second"
    Console.WriteLine( EnumMemberNames.GetName( Foo.Unnamed ) ); // "Unnamed"
}

Gratulate

If I use the above code I receive a compile error "The type 'TEnum' must be a non-nullable value type in order to use it as parameter 'TEnum' on GetNameOrNull method. – Comeback

@Comeback What line gives you that error? – Gratulate

the public static String? GetNameOrNull. If I add a where TEnum : struct, Enum then it resolves the error for me. – Comeback

@Comeback Ah, thank you - I'll correct my answer now. – Gratulate

Answer 7

    public static object GetMemberAttr(this Enum enumItem)
    {
        var memInfo = enumItem.GetType().GetMember(enumItem.ToString());
        var attr = memInfo[0].GetCustomAttributes(false);
        return attr == null || attr.Length == 0 ? null :((System.Runtime.Serialization.EnumMemberAttribute) attr[0]).Value;
    }

Usage: {YouEnum}.{EnumItem}.GetMemberAttr() public enum TEST_ENUM { [EnumMember(Value = "1min")] Minute, [EnumMember(Value = "2min")] TwoMinutes, [EnumMember(Value = "3min")] ThreeMinutes, }

public TEST_ENUM t;

? t.TwoMinutes.GetMemberAttr()
2min

Microgroove

Answer 8

Try This ,

var type = typeof(YourEnum);
var Info = type.GetMember(YourEnum.attribute); // pass enum item here
string enumdescription = Info[0].CustomAttributes.SingleOrDefault().NamedArguments[0].TypedValue.ToString();

Sorbian

Answer 9

[EnumMember] attribute is used by a serializer such as Newtonsoft.

System.Runtime.Serialization (namespace)

EnumMemberAttribute (class)

Enum:

public enum Status
{
    Pending,
    [EnumMember(Value = "In Progress")]
    InProgress,
    Failed,
    Success
}

Example code:

string databaseValue = "In Progress";

// Serialize the enum value
string statusValue = Newtonsoft.Json.JsonConvert.SerializeObject(Status.InProgress);

if  (statusValue.Contains(databaseValue))
{
    // Do something
}

Driblet

Answer 10

Wrote a simple extension method.

public static class EnumExtensions
{
    public static string ToEnumMememberAttributeValue(this Enum value)
    {
       var enumType = value.GetType();
       var enumMemeberAttribute = enumType
        .GetTypeInfo()
        .DeclaredMembers
        .Single(x => x.Name == value.ToString())
        .GetCustomAttribute<EnumMemberAttribute>(false);

        if (enumMemeberAttribute == null)
        {
            throw new NotSupportedException($"Enum: '{enumType.FullName}', value: {value} does not have attribute: '{nameof(EnumMemberAttribute)}'.");
        }

        return enumMemeberAttribute.Value;
    }

}

Sheasheaf

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