FastEnum is extremely fast enum utilities for C#/.NET. It's much faster than .NET. 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 v0.14.0, Windows 11 (10.0.22621.4037/22H2/2022Update/SunValley2)
13th Gen Intel Core i7-1360P, 1 CPU, 16 logical and 12 physical cores
.NET SDK 8.0.400
  [Host]     : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX2
  Job-CYQAVK : .NET 8.0.8 (8.0.824.36612), X64 RyuJIT AVX2

• .NET 8.0

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 toString = Fruits.Apple.FastToString();
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 toString = 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.

FastEnum is fundamentally implemented based on caching enum metadata upon its initial invocation. This approach alone achieves speeds that significantly surpass those of standard .NET, making it the optimal choice for the majority of users. Nevertheless, we acknowledge the existence of mission-critical scenarios where the ultimate pursuit of speed is paramount. To address such cases, we have introduced an API in v2 that leverages source code generation to achieve even higher performance.

[FastEnum<HttpStatusCode>]  // Annotate target enum type
partial class HttpStatusCodeBooster  // Placeholder for source code generation
{ }

var x1 = FastEnum.ToString<HttpStatusCode, HttpStatusCodeBooster>(HttpStatusCode.OK);
var x2 = FastEnum.IsDefined<HttpStatusCode, HttpStatusCodeBooster>(HttpStatusCode.OK);
var x3 = FastEnum.Parse<HttpStatusCode, HttpStatusCodeBooster>("OK");
var x4 = FastEnum.TryParse<HttpStatusCode, HttpStatusCodeBooster>("OK", out var value);

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

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

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.

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

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.

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...
[Flags]
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 16 years).

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. Furthermore, the overwhelming speed is achieved by combining the latest language features of C# with optimized code output through source code generation.

Getting started from downloading NuGet package.

dotnet add 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.