public PositionSize(PositionSizeMode mode, double value) : this() {
			Mode = mode;
			switch (Mode) {
				case PositionSizeMode.DollarsConstantForEachTrade:
					DollarsConstantEachTrade = value;
					break;
				case PositionSizeMode.SharesConstantEachTrade:
					SharesConstantEachTrade = value;
					break;
				default:
					string msg = "PositionSize: no handler for Mode[" + this.Mode + "]";
					throw new Exception(msg);
			}
		}
		public PositionSize() {
			Mode = PositionSizeMode.Unknown;
		}