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;
}

像这样的怎么样?

if (theNumber.isBetween(low, high, IntEx.Bounds.INCLUSIVE_INCLUSIVE))
{
}

扩展方法如下(已测试):

public static class IntEx
{
    public enum Bounds 
    {
        INCLUSIVE_INCLUSIVE, 
        INCLUSIVE_EXCLUSIVE, 
        EXCLUSIVE_INCLUSIVE, 
        EXCLUSIVE_EXCLUSIVE
    }

    public static bool isBetween(this int theNumber, int low, int high, Bounds boundDef)
    {
        bool result;
        switch (boundDef)
        {
            case Bounds.INCLUSIVE_INCLUSIVE:
                result = ((low <= theNumber) && (theNumber <= high));
                break;
            case Bounds.INCLUSIVE_EXCLUSIVE:
                result = ((low <= theNumber) && (theNumber < high));
                break;
            case Bounds.EXCLUSIVE_INCLUSIVE:
                result = ((low < theNumber) && (theNumber <= high));
                break;
            case Bounds.EXCLUSIVE_EXCLUSIVE:
                result = ((low < theNumber) && (theNumber < high));
                break;
            default:
                throw new System.ArgumentException("Invalid boundary definition argument");
        }
        return result;
    }
}

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;
    }

In production code I would simply write 1 <= x && x <= 100 This is easy to understand and very readable. Starting with C#9.0 we can write x is >= 1 and <= 100 Note that we must write x only once. is introduces a pattern matching expression where and is part of the pattern. && would require us to repeat x is as in x is >= 1 && x is <= 100 Here is a clever method that reduces the number of comparisons from two to one by using some math. There is not necessarily a performance advantage in doing so, but it is elegant. The idea is that one of the two factors becomes negative if the number lies outside of the range and zero if the number is equal to one of the bounds: If the bounds are inclusive: (x - 1) * (100 - x) >= 0 or (x - min) * (max - x) >= 0 If the bounds are exclusive: (x - 1) * (100 - x) > 0 or (x - min) * (max - x) > 0

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);

使用内置的Range结构体(c# 8+)，我们可以创建一个扩展方法来检查索引是否在原始范围内。

public static bool IsInRangeOf(this Range range, Index index)
{
   return index.Value >= range.Start.Value && index.Value < range.End.Value;
}

由于Index覆盖隐式操作符，因此可以传递int型而不是Index结构体。

var range = new Range(1, 10);
var isInRange = range.IsInRangeOf(1); // true, 1..10 is inclusive min range index(1)
var isInRange = range.IsInRangeOf(10); // false, 1..10 exclusive on max range index (10).
var isInRange = range.IsInRangeOf(100); // false