开关的情况下，检查范围在C＃3.5 [英] Switch case, check ranges in C# 3.5

问题描述

在C＃中，开关语句不允许的情况下跨越的值范围。我不喜欢使用的if-else循环用于此目的的想法，所以，还有没有其他方法可以检查数值范围在C＃？

In C#, the switch statement doesn't allow cases to span ranges of values. I don't like the idea of using if-else loops for this purpose, so are there any other ways to check numeric ranges in C#?

推荐答案

您可以使用的HashTable 分别为词典以创建条件= GT; 。操作

You can use a HashTable respectively Dictionary to create a mapping of Condition => Action.

例如：

class Programm
{
    static void Main()
    {
        var myNum = 12;

        var cases = new Dictionary<Func<int, bool>, Action>
        { 
            { x => x < 3 ,    () => Console.WriteLine("Smaller than 3")   } ,
            { x => x < 30 ,   () => Console.WriteLine("Smaller than 30")  } ,
            { x => x < 300 ,  () => Console.WriteLine("Smaller than 300") } 
        };

        cases.First(kvp => kvp.Key(myNum)).Value();
    }
}

这技术是一个普通的替代开关，特别是如果操作只包括一行（类似方法调用）。

This technique is a general alternative to switch, especially if the actions consists only of one line (like a method call).

和如果你迷类型别名：

using Int32Condition = System.Collections.Generic.Dictionary<System.Func<System.Int32, System.Boolean>, System.Action>;
...
    var cases = new Int32Condition()
    { 
        { x => x < 3 ,    () => Console.WriteLine("Smaller than 3")   } ,
        { x => x < 30 ,   () => Console.WriteLine("Smaller than 30")  } ,
        { x => x < 300 ,  () => Console.WriteLine("Smaller than 300") } 
    };

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