Indexing compound stat values

EntityStats.cs

    #region " Stat collection "
    [System.Serializable]
    public class Stat {

        public float Base;
        public float Modifier;
        public float Value { get { return Base + Base * Modifier; } }
    }

    protected Dictionary<StatType, Stat> _Stats = new Dictionary<StatType, Stat>();

    public float this[StatType stat, StatValueType type = StatValueType.Value] {
        get {
            switch (type) {
                case StatValueType.Base: { return _Stats[stat].Base; }
                case StatValueType.Modifier: { return _Stats[stat].Modifier; }
                default: { return _Stats[stat].Value; }
            }
        }
        set {
            if (!_Stats.ContainsKey(stat))
                _Stats.Add(stat, new Stat());

            float old = 0;
            switch (type) {

                case StatValueType.Base:
                    old = _Stats[stat].Base;
                    _Stats[stat].Base = value;
                    break;
                case StatValueType.Modifier:
                    old = _Stats[stat].Modifier;
                    _Stats[stat].Modifier = value;
                    break;
                case StatValueType.Value:
                    throw new System.InvalidOperationException("Cannot set EntityStat (" + stat.ToString() + ") value directly.  MUST set Base or Modifier instead.");
            }
            RaiseStatChanged(stat, type, old);
        }
    }

    public bool Remove(StatType stat) {
        return _Stats.Remove(stat);
    }

    #endregion