Meziantou.Framework.FastEnumGenerator

Meziantou.Framework.FastEnumGenerator

The source generator generates specialized enum helpers for selected enum types.

[assembly: FastEnumAttribute(typeof(Sample.Color), IsPublic = true, ExtensionMethodNamespace = "Sample.Extensions")]

namespace Sample
{
    public enum Color
    {
        Blue,
        Red,
        Green,
    }
}

Generated methods

For each configured enum, the generator emits these instance extension methods:

• string ToStringFast(this TEnum value)
• string ToStringFast(this TEnum value, bool useMetadata)
• bool HasFlag(this TEnum instance, TEnum flag)
• string GetName(this TEnum instance)

Method behavior:

• ToStringFast returns the declared enum name without using reflection.
• ToStringFast(..., useMetadata: true) uses metadata names when available.
• GetName is the non-metadata version of ToStringFast.
• HasFlag uses typed bitwise operations ((instance & flag) == flag).

When the target project supports C# 14 extension members, the generator also emits static members on extension(TEnum):

• TEnum Parse(string value, bool ignoreCase)
• TEnum Parse(ReadOnlySpan value, bool ignoreCase)
• TEnum Parse(string value, bool ignoreCase, bool useMetadata)
• TEnum Parse(ReadOnlySpan value, bool ignoreCase, bool useMetadata)
• bool TryParse(string value, bool ignoreCase, out TEnum result)
• bool TryParse(ReadOnlySpan value, bool ignoreCase, out TEnum result)
• bool TryParse(string value, bool ignoreCase, bool useMetadata, out TEnum result)
• bool TryParse(ReadOnlySpan value, bool ignoreCase, bool useMetadata, out TEnum result)
• bool IsDefined(TEnum value)
• ReadOnlySpan GetNames(bool useMetadata)
• ReadOnlySpan GetValues()

Analyzer rules

The package also ships analyzers and code fixes for enums configured with FastEnumAttribute.

Metadata names

useMetadata uses names from:

• DisplayAttribute.Name
• DisplayNameAttribute.DisplayName
• EnumMemberAttribute.Value

When metadata is not available for a member, the declared enum name is used.

Additional resources

• Caching Enum.ToString to improve performance