Using an && expression to join two comparisons is simply the most elegant way to do this. If you try using fancy extension methods and such, you run into the question of whether to include the upper bound, the lower bound, or both. Once you start adding additional variables or changing the extension names to indicate what is included, your code becomes longer and harder to read (for the vast majority of programmers). Furthermore, tools like Resharper will warn you if your comparison doesn't make sense (number > 100 && number < 1), which they won't do if you use a method ('i.IsBetween(100, 1)').

我要做的唯一另一个评论是，如果你检查输入的意图是抛出异常，你应该考虑使用代码契约:

Contract.Requires(number > 1 && number < 100)

这比if(…)抛出new Exception(…)更优雅，如果有人试图调用您的方法而没有首先确保该数字在边界内，您甚至可以得到编译时警告。

在c#中，关于速度和代码原的最佳解决方案，只有一次比较，没有约束检查，并且不会因溢出而容易出错:

public static bool IsInRange(int value, int min, int max) => (uint)(value - min) <= (uint)(max - min);

最小值和最大值包括在内。

In C, if time efficiency is crucial and integer overflows will wrap, one could do if ((unsigned)(value-min) <= (max-min)) .... If 'max' and 'min' are independent variables, the extra subtraction for (max-min) will waste time, but if that expression can be precomputed at compile time, or if it can be computed once at run-time to test many numbers against the same range, the above expression may be computed efficiently even in the case where the value is within range (if a large fraction of values will be below the valid range, it may be faster to use if ((value >= min) && (value <= max)) ... because it will exit early if value is less than min).

不过，在使用这样的实现之前，请先对目标机器进行基准测试。在某些处理器上，由两部分组成的表达式可能在所有情况下都更快，因为两个比较可能是独立完成的，而在减法和比较方法中，减法必须在比较执行之前完成。

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
        }

只是为了增加这里的噪音，你可以创建一个扩展方法:

public static bool IsWithin(this int value, int minimum, int maximum)
{
    return value >= minimum && value <= maximum;
}

这样你就能做…

int val = 15;

bool foo = val.IsWithin(5,20);

话虽如此，当检查本身只有一行时，这样做似乎是一件愚蠢的事情。

因为所有其他答案都不是我发明的，这里只是我的实现:

public enum Range
{
    /// <summary>
    /// A range that contains all values greater than start and less than end.
    /// </summary>
    Open,
    /// <summary>
    /// A range that contains all values greater than or equal to start and less than or equal to end.
    /// </summary>
    Closed,
    /// <summary>
    /// A range that contains all values greater than or equal to start and less than end.
    /// </summary>
    OpenClosed,
    /// <summary>
    /// A range that contains all values greater than start and less than or equal to end.
    /// </summary>
    ClosedOpen
}

public static class RangeExtensions
{
    /// <summary>
    /// Checks if a value is within a range that contains all values greater than start and less than or equal to end.
    /// </summary>
    /// <param name="value">The value that should be checked.</param>
    /// <param name="start">The first value of the range to be checked.</param>
    /// <param name="end">The last value of the range to be checked.</param>
    /// <returns><c>True</c> if the value is greater than start and less than or equal to end, otherwise <c>false</c>.</returns>
    public static bool IsWithin<T>(this T value, T start, T end) where T : IComparable<T>
    {
        return IsWithin(value, start, end, Range.ClosedOpen);
    }

    /// <summary>
    /// Checks if a value is within the given range.
    /// </summary>
    /// <param name="value">The value that should be checked.</param>
    /// <param name="start">The first value of the range to be checked.</param>
    /// <param name="end">The last value of the range to be checked.</param>
    /// <param name="range">The kind of range that should be checked. Depending on the given kind of range the start end end value are either inclusive or exclusive.</param>
    /// <returns><c>True</c> if the value is within the given range, otherwise <c>false</c>.</returns>
    public static bool IsWithin<T>(this T value, T start, T end, Range range) where T : IComparable<T>
    {
        if (value == null)
            throw new ArgumentNullException(nameof(value));

        if (start == null)
            throw new ArgumentNullException(nameof(start));

        if (end == null)
            throw new ArgumentNullException(nameof(end));

        switch (range)
        {
            case Range.Open:
                return value.CompareTo(start) > 0
                       && value.CompareTo(end) < 0;
            case Range.Closed:
                return value.CompareTo(start) >= 0
                       && value.CompareTo(end) <= 0;
            case Range.OpenClosed:
                return value.CompareTo(start) > 0
                       && value.CompareTo(end) <= 0;
            case Range.ClosedOpen:
                return value.CompareTo(start) >= 0
                       && value.CompareTo(end) < 0;
            default:
                throw new ArgumentException($"Unknown parameter value {range}.", nameof(range));
        }
    }
}

然后你可以这样使用它:

var value = 5;
var start = 1;
var end = 10;

var result = value.IsWithin(start, end, Range.Closed);