简单工厂模式

public class Operateion{private double _numberA;private double _numberB;public double NumberA{get{return _numberA;}set{_numberA = value;}}public double NumberB{get{return _numberB;}set{_numberB = value;}}public virtual double GetResult(){double result = 0;return result;}}class OperationAdd : Operation{public override double GetResult(){double result = 0;result = NumberA + NumberB;return result;}}class OperationSub : Opeartion{public override double GetResutl(){double result = 0;result = NumberA - NumberB;return result;}}

public class OperationFactory{public static Operation createOperation(string operate){Operation oper = null;switch(operate){case "+":oper = new OperationAdd();break;case "-":oper = new OperationSub();break;}return oper;}}