EnumUtils.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace Ogxd;

/// <summary>
/// Returns a string for a given enum value, without allocations
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="value"></param>
/// <returns></returns>
public static string ToStringCached<T>(this T value) where T : Enum => EnumLabelsCache<T>.GetLabel(value);

/// <summary>
/// Returns all string labels for a given enum, without allocations
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static IEnumerable<string> GetEnumLabels<T>() where T : Enum => EnumLabelsCache<T>.Labels;

/// <summary>
/// Returns all values for a given enum, without allocations
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static IEnumerable<T> GetEnumValues<T>() where T : Enum => EnumLabelsCache<T>.Values;

private static class EnumLabelsCache<T> where T : Enum
{
    private static Dictionary<T, string> _labels;

    static EnumLabelsCache()
    {
        IEnumerable<T> values = Enum.GetValues(typeof(T)).Cast<T>();
        _labels = values.ToDictionary(t => t, t => t.ToString());
    }

    internal static string GetLabel(T value) => _labels[value];
    internal static IEnumerable<string> Labels => _labels.Values;
    internal static IEnumerable<T> Values => _labels.Keys;
}