C#中使用委託、接口、匿名方法、泛型委託實現加減乘除算法

 

使用C#實現加減乘除算法常常被用做新手練習。本篇來分別體驗經過委託、接口、匿名方法、泛型委託來實現。


算法

使用委託實現


加減乘除擁有相同的參數個數、類型和返回類型,首先想到了使用委託實現。ide

 

//建立一個委託
public delegate decimal MathOperation(decimal left, decimal right);

//建立方法參數和返回結果符合委託的定義
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;
}

//返回委託類型
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做數和符號考慮進來,返回委託類型
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 +"));
}

 

使用接口實現


以上,委託用在了方法層面。若是在類層面,也可用接口封裝加減乘除的共性。spa

 

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


委託還能夠結合匿名方法一塊兒使用。code

 

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("");
}

 

泛型委託


而用泛型委託實現更簡潔。blog

 

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("");
}

 

暫時這些。接口

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