使用委托實現

加減乘除擁有相同的參數個數、類型和返回類型，首先想到了使用委托實現。

//創建一個委托 public delegate decimal MathOperation(decimal left, decimal right);//創建方法參數和返回結果符合委托的定義 public static decimal Add(decimal left, decimal right) {return left + right; }public static decimal Subtract(decimal left, decimal right) {return left - right; }public static decimal Multiply(decimal left, decimal right) {return left * right; }public static decimal Divide(decimal left, decimal right) {return left / right; }//返回委托類型 private static MathOperation GetOperation(char oper) {switch(oper){case '+': return Add;case '-': return Subtract;case '*': return Multiply;case '/': return Divide;}throw new NotSupportedException(""); }//封裝一個方法用來把操作數和符號考慮進來,返回委托類型 private static decimal Eval(string expr) {var elements = expr.Split(new []{' '}, 3);var left = Decimal.Parse(elements[0]);var right = Decimal.Parse(elements[1]);var ope = elements[2][0];return GetOperation(op)(left, right); }void Main() {Console.WriteLine(Eval("1 3 +")); }

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使用接口實現

以上，委托用在了方法層面。如果在類層面，也可用接口封裝加減乘除的共性。

public interface IMathOperation {decimal Compute(decimal left, decimal right); }public class AddOperation : IMathOperation {decimal Compute(decimal left, decimal right){return left + right;} }public class SubtractOperation : IMathOperation {decimal Compute(decimal left,, decimal right){return left - right;} }public class MultiplyOperation : IMathOperation {decimal Compute(decimal left, decimal right){return left * right;} }public class DivideOperation : IMathOperation {decimal Compute(decimal left, decimal right){return left/right;} }//獲取接口類型 private static IMathOperation GetOperation(char oper) {switch(oper){case '+': return new AddOperation();case '-': return new SubtractOperation();case '*': return new MultiplyOperation();case '/': return new DivideOperation();}throw new NotSupportedException(""); }...

使用匿名方法

委托還可以結合匿名方法一起使用

public delegate decimal MathOperation(decimal left, decimal right);private static MathOperation GetOperation(char oper) {switch(oper){case '+': return delgate(decimal left, decimal right) {return left + right;};case '-': return delgate(decimal left, decimal right) {return left - right;};case '*': return delgate(decimal left, decimal right) {return left * right;};case '/': return delgate(decimal left, decimal right) {return left / right;};}throw new NotSupportedException(""); }

泛型委托

而用泛型委托實現更簡潔。

private static Func<decimal, decimal, decimal> GetOperation(char oper) {switch(oper){case '+': return (left, right) => left + right;case '-': return (left, right) => left - right;case '*': return (left, right) => left * right;case '/': return (left, right) => left / right;}throw new NotSupportedExcepton(""); }

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轉載于:https://www.cnblogs.com/shy1766IT/p/5490992.html

總結

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