EnumSnakeCaseExtensions.cs

using System;
using System.Text.RegularExpressions;

    public static class EnumSnakeCaseExtensions
    {
        public static string ToSnakeCase(this Enum value)
        {
            return Regex.Replace(value.ToString(), @"(\p{Ll})(\p{Lu})", "$1_$2").ToLower();
        }

        public static T FromSnakeCase<T>(this string value) where T : struct
        {
            if (!typeof(T).IsEnum)
            {
                throw new NotSupportedException("T must be an Enum type");
            }

            var pascalCase = Regex.Replace(value, @"(-|_)\w{1}|^\w",
                match => match.Value.Replace("-", string.Empty).Replace("_", string.Empty).ToUpper());
            return (T)Enum.Parse(typeof(T), pascalCase);
        }
    }