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FastEnum is the fastest enum utilities for C#/.NET. It's much faster than .NET Core, and also faster than Enums.NET that is similar library. Provided methods are all achieved zero allocation and are designed easy to use like System.Enum. This library is quite useful to significantly improve your performance because enum is really popular feature.




BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19042
Intel Core i7-8565U CPU 1.80GHz (Whiskey Lake), 1 CPU, 8 logical and 4 physical cores
.NET Core SDK=5.0.100
  [Host]   : .NET Core 5.0.0 (CoreCLR, CoreFX, X64 RyuJIT
  ShortRun : .NET Core 5.0.0 (CoreCLR, CoreFX, X64 RyuJIT

Support Platform

  • .NET Framework 4.6.1+
  • .NET Standard 2.0+
  • .NET 5.0+

How to use

This library super easy to use like System.Enum that is standard of .NET. Look below:

//--- FastEnum
var values = FastEnum.GetValues<Fruits>();
var names = FastEnum.GetNames<Fruits>();
var name = FastEnum.GetName<Fruits>(Fruits.Apple);
var name = Fruits.Apple.ToName();
var defined = FastEnum.IsDefined<Fruits>(123);
var parse = FastEnum.Parse<Fruits>("Apple");
var tryParse = FastEnum.TryParse<Fruits>("Apple", out var value);
//--- .NET
var values = Enum.GetValues(typeof(Fruits)) as Fruits[];
var names = Enum.GetNames(typeof(Fruits));
var name = Enum.GetName(typeof(Fruits), Fruits.Apple);
var name = Fruits.Apple.ToString();
var defined = Enum.IsDefined(typeof(Fruits), 123);
var parse = Enum.Parse<Fruits>("Apple");
var tryParse = Enum.TryParse<Fruits>("Apple", out var value);

As you can see, the replacement from System.Enum is very easy. You never confuse.

More features

There are some functions that are often used for enum, and you can be used more conveniently by including them together.

1. Gets pairwised member information

Sometimes you want name / value pair of enum. Member<TEnum> can be used under such cases. Of course supports deconstruction feature. FieldInfo is also included, so please use it for reflection code.

class Member<TEnum>
    public TEnum Value { get; }
    public string Name { get; }
    public FieldInfo FieldInfo { get; }
    // etc...

var member = Fruits.Apple.ToMember();
var (name, value) = member;  // Supports deconstruction

2. Gets EnumMemberAttribute.Value

I often see the developer using EnumMemberAttribute as an alias for field name. So FastEnum provides an API that the value can be quickly obtained from the EnumMemberAttribute.Value property.

enum Company
    [EnumMember(Value = "Apple, Inc.")]
    Apple = 0,

var value = Company.Apple.GetEnumMemberValue();  // Apple, Inc.

3. Adds multiple label annotations to a field

Multiple attributes can’t be attached to the same field, since EnumMemberAttribute is specified AllowMultiple = false. It’s inconvenient and I don’t like it personally, so I often use my own LabelAttribute as an alternative. You can use it conveniently as follows, because FastEnum provides this feature.

enum Company
    [Label("Apple, Inc.")]
    [Label("AAPL", 1)]
    Apple = 0,

var x1 = Company.Apple.GetLabel();   // Apple, Inc.
var x2 = Company.Apple.GetLabel(1);  // AAPL


1. Provides only generics API

FastEnum provides only generics version method because of performance reason. System.Enum provides System.Type argument overload, but that’s too slow because of boxing occuration. If you need to use the method that passes System.Type type, please use System.Enum version.

2. Can’t parse comma-separated string

System.Enum.Parse can parse like following string. I think that it isn’t well known because it is a specification that exists quietly.

//--- Assuming there is an enum type like following...
enum Fruits
    Apple = 1,
    Lemon = 2,
    Melon = 4,
    Banana = 8,

//--- Passes comma-separated string
var value = Enum.Parse<Fruits>("Apple, Melon");
Console.WriteLine((int)value);  // 5

It seems to be a useful function when performing flag processing, but if tries to add such a comma-separated analysis, the overhead will come out, so cutting this feature off makes speed up. I think that in most cases there is no problem, because this feature is rarely used (at least I have NEVER used for 12 years).

Why fast ?

As you might expect, it’s because cached internally. It takes the approach of Static Type Caching, so the reading cost is almost zero. Based on this, I use techniques for avoiding allocation, and create specialized dictionary for specific key internally.


Getting started from downloading NuGet package.

dotnet add package FastEnum
PM> Install-Package FastEnum


This library is provided under MIT License.


Takaaki Suzuki (a.k.a @xin9le) is software developer in Japan who awarded Microsoft MVP for Developer Technologies (C#) since July 2012.

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