gistfile1.cs

public static class EnumUtils
{
        public static IEnumerable<T> Values<T>()
        {
            CheckTypeParamIsEnum<T>(); 
            
            return Enum.GetValues(typeof(T)).Cast<T>();
        }

        public static T ToEnum<T>(int value)
        {
            CheckTypeParamIsEnum<T>();

            Ensure.ArgumentValid(Enum.IsDefined(typeof(T), value), 
                "value", 
                value + " is not a valid value for enumeration " + typeof(T));
            return (T) Enum.ToObject(typeof(T), value);
        }

        public static T Parse<T>(string value)
        {
            CheckTypeParamIsEnum<T>();

            return (T) Enum.Parse(typeof(T), value);
        }

        public static T? ParseNullable<T>(string value) where T : struct 
        {
            CheckTypeParamIsEnum<T>();

            if(Enum.IsDefined(typeof(T), value))
            {
                return (T) Enum.Parse(typeof(T), value);
            }
            return null;
        }

        private static void CheckTypeParamIsEnum<T>()
        {
            if (!(typeof(Enum).IsAssignableFrom(typeof(T))))
            {
                throw new ArgumentException("Enum type expected");
            }
        }
}