我如何用c#优雅地做到这一点?

例如,一个数字可以是1到100之间。

我知道一个简单的if (x >= 1 && x <= 100)就足够了;但是有很多语法糖和新特性不断添加到c# /。Net这个问题是关于更习惯的(一个可以称之为优雅的)写法。

性能不是问题,但请在非O(1)的解决方案中添加性能说明,因为人们可能会复制粘贴建议。


当前回答

你在寻找[1..100]?这只是帕斯卡。

其他回答

我使用下一个“优雅”的解决方案:

using static System.Linq.Enumerable;

int x = 30;
if (Range(1,100).Contains(x))  //true

来自微软文档

using static指令适用于任何具有静态成员(或嵌套类型)的类型,即使它也具有实例成员。但是,实例成员只能通过类型实例调用。

你可以访问一个类型的静态成员,而不需要用类型名限定访问:

但这对许多人来说并不简单,因为Enumerable。Range有第一个参数start和第二个参数count。 所以这种检查可能在特定情况下有用,比如当你使用Enumerable时。范围的foreach循环,在开始之前,您想知道,如果循环将执行。

例如:

        int count = 100;
        int x = 30;

        if (!Range(1, count).Contains(x)) {
            Console.WriteLine("Do nothing!");
            return;
        }

        foreach (var i in Range(1, count)) {
            // Some job here
        }

关于优雅,最接近数学符号(a <= x <= b)的方法略微提高了可读性:

public static bool IsBetween(this int value, int min, int max)
{
    return min <= value && value <= max;
}

为了进一步说明:

public static bool IsOutside(this int value, int min, int max)
{
    return value < min || max < value;
}

有很多选择:

int x = 30;
if (Enumerable.Range(1,100).Contains(x))  //true

实际上,基本的,如果更优雅的话,可以在第一张支票中用倒序写:

if (1 <= x && x <= 100)   //true

此外,查看这篇SO帖子的正则表达式选项。

注:

LINQ solution is strictly for style points - since Contains iterates over all items its complexity is O(range_size) and not O(1) normally expected from a range check. More generic version for other ranges (notice that second argument is count, not end): if (Enumerable.Range(start, end - start + 1).Contains(x) There is temptation to write if solution without && like 1 <= x <= 100 - that look really elegant, but in C# leads to a syntax error "Operator '<=' cannot be applied to operands of type 'bool' and 'int'"

如果你想写更多的代码而不是简单的If,也许你可以: 创建一个名为IsBetween的扩展方法

public static class NumberExtensionMethods
{
    public static bool IsBetween(this long value, long Min, long Max)
    {
        // return (value >= Min && value <= Max);
        if (value >= Min && value <= Max) return true;
        else return false;
    }
}

...

// Checks if this number is between 1 and 100.
long MyNumber = 99;
MessageBox.Show(MyNumber.IsBetween(1, 100).ToString());

Addendum: it's worth noting that in practice you very rarely "just check for equality" (or <, >) in a codebase. (Other than in the most trivial situations.) Purely as an example, any game programmer would use categories something like the following in every project, as a basic matter. Note that in this example it (happens to be) using a function (Mathf.Approximately) which is built in to that environment; in practice you typically have to carefully develop your own concepts of what comparisons means for computer representations of real numbers, for the type of situation you are engineering. (Don't even mention that if you're doing something like, perhaps a controller, a PID controller or the like, the whole issue becomes central and very difficult, it becomes the nature of the project.) BY no means is the OP question here a trivial or unimportant question.

private bool FloatLessThan(float a, float b)
    {
    if ( Mathf.Approximately(a,b) ) return false;
    if (a<b) return true;
    return false;
    }

private bool FloatLessThanZero(float a)
    {
    if ( Mathf.Approximately(a,0f) ) return false;
    if (a<0f) return true;
    return false;
    }

private bool FloatLessThanOrEqualToZero(float a)
    {
    if ( Mathf.Approximately(a,0f) ) return true;
    if (a<0f) return true;
    return false;
    }

好吧,我会配合的。已经有这么多答案了,但也许还有一些其他新奇的空间:

(显然你根本不用这些)

    var num = 7;
    const int min = 5;
    const int max = 10;
    var inRange = Math.Clamp(num, min, max) == num;

Or

    var num = 7;
    const int min = 5;
    const int max = 10;
    var inRange = num switch { < min => false, > max => false, _ => true };

Or

    var num = 7;
    const int min = 5;
    const int max = 10;
    var inRange = num is >= min and <= max;

好吧,也许你可以用最后一个。

好的,再来一个

    var num = 7;
    const int min = 5;
    const int max = 10;
    var inRange = Enumerable.Range(min, max-min).Contains(num);