设计模式——简单工厂模式

面向对象——如：活字印刷术 封装、继承、多态

通过面向对象的三大特性：封装、继承、多态 降低程序耦合度。使得程序易维护、易扩展、易复用

松耦合——业务逻辑与界面逻辑分离——简单工厂模式

例如构建一个计算器功能：
1.根据计算方式，只编译该类型与方法，而不是编译所有，易于维护。例如：使用加法运算只编译加法运算而不是所有运算。
2.添加其他运算方式。例如添加次方运算，不用给工程师整个代码，发生其他计算方式代码误操作、更改、泄密等其他情况。
以下分别举例紧耦合案列、松耦合案例：

紧耦合举例

所有方法汇总在一起，导致计算时需要全部加载

       public void TryCal(){try{//输入数字A:string strNumberA = numberA.Text;//请选择运算符号(+、-、*、/)string strOperate = numberO.Text;//请输入数字B:string strNumberB = numberB.Text;numberR.Text = operation.GetResult(Convert.ToDouble(strNumberA), Convert.ToDouble(strNumberB), strOperate).ToString();}catch (Exception er){LBError.Content = er.Message.ToString();}}public class operation{public static double GetResult(double A, double B, string operatesign){double result = 0d;switch (operatesign){case "+":result = A + B;break;case "-":result = A - B;break;case "*":result = A * B;break;case "/":result = A / B;break;default:break;}return result;}}private void numberR_KeyDown(object sender, KeyEventArgs e){if (e.Key==Key.Enter){TryCal();}}

松耦合举例——简单工厂模式

利用简单工厂模式，根据条件实例化对象，避免增加不必要的实例化对象。

       public void TryCall_Factory(){try{operationL opel = OperationFactory.createOperate(numberO.Text);opel.NumberA = Convert.ToDouble(numberA.Text);opel.NumberB = Convert.ToDouble(numberB.Text);numberR.Text = opel.Getresult().ToString();}catch (Exception er){LBError.Content = er.Message.ToString();}}public class OperationFactory{public static operationL createOperate(string operatestr){operationL operation = null;switch (operatestr){case "+":operation = new OperationAdd();break;case "-":operation = new OperationSub();break;case "*":operation = new OperationMul();break;case "/":operation = new OperationDiv();break;}return operation;}}public class operationL{private Double _numberA;public Double NumberA{get { return _numberA; }set { _numberA = value; }}private Double _numberB;public Double NumberB{get { return _numberB; }set { _numberB = value; }}public virtual Double Getresult(){double result = 0d;return result;}}public class OperationAdd:operationL{public override double Getresult(){double result = 0d;result = NumberA + NumberB;return result;}}public class OperationSub : operationL{public override double Getresult(){double result = 0d;result = NumberA - NumberB;return result;}}public class OperationMul : operationL{public override double Getresult(){double result = 0d;result = NumberA* NumberB;return result;}}public class OperationDiv : operationL{public override double Getresult(){double result = 0d;if (NumberB == 0)throw new Exception("除数不能为0");result = NumberA /NumberB;return result;}}