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。
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
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);
其他回答
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。
您可以使用模式匹配以最优雅的方式实现这一点:
int i = 5;
if(i is (>0 and <=10))
{
}
if (value > 1 && value < 100)
{
// do work
}
else
{
// handle outside of range logic
}
优雅是因为它不需要确定两个边界值中哪个先大。它也不包含分支。
public static bool InRange(float val, float a, float b)
{
// Determine if val lies between a and b without first asking which is larger (a or b)
return ( a <= val & val < b ) | ( b <= val & val < a );
}
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);