using System;

using System.Collections.Generic;

using System.Linq;

#nullable enable

​

public class Program

{

    public static void Main()

    {

        // Integers that don't exist in the enum can still be converted to the enum type.

        ColorValue badColorValue = (ColorValue)int.MaxValue;

        Console.WriteLine($"Not really a color value, so the result is null: {(badColorValue?.ToString() ?? "[NULL]")}");

        // Integers are initialized as 0, which may not exist in the enum type.

        ColorValue defaultColorValue = default(ColorValue);

        Console.WriteLine($"The underlying value is 0 which isn't defined in the list, so the result is null: {(defaultColorValue?.ToString() ?? "[NULL]")}");

        ColorValue goodColorValue = (ColorValue)"Green";

        Console.WriteLine($"Green is a valid color value: {(goodColorValue?.ToString() ?? "[NULL]")}");

    }

    class ColorValue

    {

        public static readonly ColorValue Default = new ColorValue { Id = -1, Name = "Black" };

        public static readonly ColorValue Blue = new ColorValue { Id = 1, Name = "Blue" };

        public static readonly ColorValue Green = new ColorValue { Id = 2, Name = "Green" };

        public static readonly ColorValue White = new ColorValue { Id = 3, Name = "White" };

        private static readonly Lazy<IEnumerable<ColorValue>> _values = new(() => new List<ColorValue>() { Default, Blue, Green, White });

        public int Id { get; set; }

        public string? Name { get; set; }

        public string? Description { get; set; }

        public static explicit operator ColorValue(int id)

        {

            return _values!.Value.FirstOrDefault(x => x.Id == id);

        }

        public static explicit operator ColorValue(string name)

        {

            return _values!.Value.FirstOrDefault(x => x.Name == name);

        }

        public override string ToString() {

            return this.Name;

        }

    }

}

​

​