gistfile1.cs

    public class ValueObjectHolder: DomainEntity    
    {
        protected ValueObjectHolder()
        {
            Values = new List<ValueObject>();
        }

        public ValueObjectHolder(string key):this()
        {
            Key = key;
        }

        public virtual string Key { get; protected set; }

        public virtual IList<ValueObject> Values { get; set; }

        public virtual ValueObjectHolder AddValueObject(ValueObject valueObject)
        {
            if (Key.IsEmpty())
                throw new InvalidOperationException(
                    "You must specify the ValueObject Key before you can add a child value");
            valueObject.Parent = this;
            valueObject.Key = string.Format("{0}=>{1}", Key, valueObject.Key);
            Values.Add(valueObject);
            return this;
        }
    }

    public class ValueObject : DomainEntity
    {
        protected ValueObject()
        {
        }

        public ValueObject(string key) : this()
        {
            if (key.IsEmpty())
                throw new InvalidOperationException("You must specify the ValueObject Key");
            Key = key;
            Value = key;
        }

        [NotNullNotEmpty]
        public virtual string Key { get;  set; }

        [NotNullNotEmpty]
        public virtual string Value { get; set; }

        public virtual bool IsDefault { get; set; }
        
        public virtual ValueObjectHolder Parent { get; set; }

        public virtual string GetKey()
        {
            var indexOfLastDelimeter = Key.LastIndexOf("=>") + 2;
            if (indexOfLastDelimeter == 2) return Key;
            
            return Key.Substring(indexOfLastDelimeter, Key.Length-indexOfLastDelimeter);
        }

    }