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
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
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);
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);
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
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);
我不知道,但我用这个方法:
public static Boolean isInRange(this Decimal dec, Decimal min, Decimal max, bool includesMin = true, bool includesMax = true ) {
return (includesMin ? (dec >= min) : (dec > min)) && (includesMax ? (dec <= max) : (dec < max));
}
这是我使用它的方式:
[TestMethod]
public void IsIntoTheRange()
{
decimal dec = 54;
Boolean result = false;
result = dec.isInRange(50, 60); //result = True
Assert.IsTrue(result);
result = dec.isInRange(55, 60); //result = False
Assert.IsFalse(result);
result = dec.isInRange(54, 60); //result = True
Assert.IsTrue(result);
result = dec.isInRange(54, 60, false); //result = False
Assert.IsFalse(result);
result = dec.isInRange(32, 54, false, false);//result = False
Assert.IsFalse(result);
result = dec.isInRange(32, 54, false);//result = True
Assert.IsTrue(result);
}