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

如果是为了验证方法参数,没有一个解决方案会抛出argumentoutofranceexception,并允许简单/适当地配置包含/排除的最小/最大值。

像这样使用

public void Start(int pos)
{
    pos.CheckRange(nameof(pos), min: 0);

    if (pos.IsInRange(max: 100, maxInclusive: false))
    {
        // ...
    }
}

我只是写出了这些漂亮的函数。它还具有对有效值没有分支(单个if)的优点。最难的部分是制作适当的异常消息。

/// <summary>
/// Returns whether specified value is in valid range.
/// </summary>
/// <typeparam name="T">The type of data to validate.</typeparam>
/// <param name="value">The value to validate.</param>
/// <param name="min">The minimum valid value.</param>
/// <param name="minInclusive">Whether the minimum value is valid.</param>
/// <param name="max">The maximum valid value.</param>
/// <param name="maxInclusive">Whether the maximum value is valid.</param>
/// <returns>Whether the value is within range.</returns>
public static bool IsInRange<T>(this T value, T? min = null, bool minInclusive = true, T? max = null, bool maxInclusive = true)
    where T : struct, IComparable<T>
{
    var minValid = min == null || (minInclusive && value.CompareTo(min.Value) >= 0) || (!minInclusive && value.CompareTo(min.Value) > 0);
    var maxValid = max == null || (maxInclusive && value.CompareTo(max.Value) <= 0) || (!maxInclusive && value.CompareTo(max.Value) < 0);
    return minValid && maxValid;
}

/// <summary>
/// Validates whether specified value is in valid range, and throws an exception if out of range.
/// </summary>
/// <typeparam name="T">The type of data to validate.</typeparam>
/// <param name="value">The value to validate.</param>
/// <param name="name">The name of the parameter.</param>
/// <param name="min">The minimum valid value.</param>
/// <param name="minInclusive">Whether the minimum value is valid.</param>
/// <param name="max">The maximum valid value.</param>
/// <param name="maxInclusive">Whether the maximum value is valid.</param>
/// <returns>The value if valid.</returns>
public static T CheckRange<T>(this T value, string name, T? min = null, bool minInclusive = true, T? max = null, bool maxInclusive = true)
where T : struct, IComparable<T>
{
    if (!value.IsInRange(min, minInclusive, max, maxInclusive))
    {
        if (min.HasValue && minInclusive && max.HasValue && maxInclusive)
        {
            var message = "{0} must be between {1} and {2}.";
            throw new ArgumentOutOfRangeException(name, value, message.FormatInvariant(name, min, max));
        }
        else
        {
            var messageMin = min.HasValue ? GetOpText(true, minInclusive).FormatInvariant(min) : null;
            var messageMax = max.HasValue ? GetOpText(false, maxInclusive).FormatInvariant(max) : null;
            var message = (messageMin != null && messageMax != null) ?
                "{0} must be {1} and {2}." :
                "{0} must be {1}.";
            throw new ArgumentOutOfRangeException(name, value, message.FormatInvariant(name, messageMin ?? messageMax, messageMax));
        }
    }
    return value;
}

private static string GetOpText(bool greaterThan, bool inclusive)
{
    return (greaterThan && inclusive) ? "greater than or equal to {0}" :
        greaterThan ? "greater than {0}" :
        inclusive ? "less than or equal to {0}" :
        "less than {0}";
}

public static string FormatInvariant(this string format, params object?[] args) => string.Format(CultureInfo.InvariantCulture, format, args);

其他回答

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

if (value > 1 && value < 100)
{
    // do work
}
else
{
    // handle outside of range logic
}

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);

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。

这些是一些可以提供帮助的扩展方法

  public static bool IsInRange<T>(this T value, T min, T max)
where T : System.IComparable<T>
    {
        return value.IsGreaterThenOrEqualTo(min) && value.IsLessThenOrEqualTo(max);
    }


    public static bool IsLessThenOrEqualTo<T>(this T value, T other)
         where T : System.IComparable<T>
    {
        var result = value.CompareTo(other);
        return result == -1 || result == 0;
    }


    public static bool IsGreaterThenOrEqualTo<T>(this T value, T other)
         where T : System.IComparable<T>
    {
        var result = value.CompareTo(other);
        return result == 1 || result == 0;
    }