How to elegantly check if a number is within a range?

Question

How can I do this elegantly with C#?

For example, a number can be between 1 and 100.

I know a simple if (x >= 1 && x <= 100) would suffice; but with a lot of syntax sugar and new features constantly added to C#/.Net this question is about more idiomatic (one can all it elegance) ways to write that.

Performance is not a concern, but please add performance note to solutions that are not O(1) as people may copy-paste the suggestions.

Answer 1

There are a lot of options:

int x = 30;
if (Enumerable.Range(1,100).Contains(x))  //true

And indeed basic if more elegantly can be written with reversing order in the first check:

if (1 <= x && x <= 100)   //true

Also, check out this SO post for regex options.

Notes:

• LINQ solution is strictly for style points - since Contains iterates over all items its complexity is O(range_size) and not O(1) normally expected from a range check.
  More generic version for other ranges (notice that second argument is count, not end):

  if (Enumerable.Range(start, end - start + 1).Contains(x)
  

• There is temptation to write if solution without && like 1 <= x <= 100 - that look really elegant, but in C# leads to a syntax error "Operator '<=' cannot be applied to operands of type 'bool' and 'int'"

Answer 2

1. In production code I would simply write

   1 <= x && x <= 100

   This is easy to understand and very readable.

2. 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

3. 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
   

Answer 3

Do you mean?

if(number >= 1 && number <= 100)

or

bool TestRange (int numberToCheck, int bottom, int top)
{
  return (numberToCheck >= bottom && numberToCheck <= top);
}

Answer 4

Just to add to the noise here, you could create an extension method:

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

Which would let you do something like...

int val = 15;

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

That being said, this seems like a silly thing to do when the check itself is only one line.

Answer 5

As others said, use a simple if.

You should think about the ordering.

e.g

1 <= x && x <= 100

is easier to read than

x >= 1 && x <= 100

Answer 6

I propose this:

public static bool IsWithin<T>(this T value, T minimum, T maximum) where T : IComparable<T> {
    if (value.CompareTo(minimum) < 0)
       return false;
    if (value.CompareTo(maximum) > 0)
       return false;
    return true;
}

Examples:

45.IsWithin(32, 89)
true
87.2.IsWithin(87.1, 87.15)
false
87.2.IsWithin(87.1, 87.25)
true

and of course with variables:

myvalue.IsWithin(min, max)

It's easy to read (close to human language) and works with any comparable type (integer, double, custom types...).

Having code easy to read is important because the developer will not waste "brain cycles" to understand it. In long coding sessions wasted brain cycles make developer tired earlier and prone to bug.

Answer 7

With a bit of extension method abuse, we can get the following "elegant" solution:

using System;

namespace Elegant {
    public class Range {
        public int Lower { get; set; }
        public int Upper { get; set; }
    }

    public static class Ext {
        public static Range To(this int lower, int upper) {
            return new Range { Lower = lower, Upper = upper };
        }

        public static bool In(this int n, Range r) {
            return n >= r.Lower && n <= r.Upper;
        }
    }

    class Program {
        static void Main() {
            int x = 55;
            if (x.In(1.To(100)))
                Console.WriteLine("it's in range! elegantly!");
        }
    }
}

Answer 8

If this is incidental, a simple if is all you need. If this happens in many places, you might want to consider these two:

• PostSharp. Decorate methods with attributes that 'inject' code into the method after compilation. I don't know for sure, but I can imagine it can be used for this.

Something like:

[Between("parameter", 0, 100)]
public void Foo(int parameter)
{
}

• Code contracts. Has the advantage that the constraints can be checked at compile time, by static verification of your code and the places that use your code.

Answer 9

EDIT: New Answer provided. I was just starting out using C# when I wrote the first answer to this question, and in hindsight I now realize that my "solution" was / is naive and inefficient.

My original answer: I'd go with the more simple version:

`if(Enumerable.Range(1,100).Contains(intInQuestion)) { ...DoStuff; }`

A Better Way

As I haven't seen any other solution that is more efficient (according to my tests at least), I'll give it another go.

New and better way that also works with negative ranges:

// Returns true if x is in range [min..max], else false 
bool inRange(int x, int min=1, int max=100) => ((x - max)*(x - min) <= 0);

This can be used with both positive and negative ranges and defaults to a range of

1..100 (inclusive) and uses x as the number to check followed by an optional range defined by min and max.

Adding Examples For Good Measure

Example 1:

// Returns true if x is in range [min..max], else false 
bool inRange(int x, int min=1, int max=100) => ((x - max)*(x - min) <= 0);

Console.WriteLine(inRange(25));
Console.WriteLine(inRange(1));
Console.WriteLine(inRange(100));
Console.WriteLine(inRange(25, 30, 150));
Console.WriteLine(inRange(-25, -50, 0));

Returns:

True
True
True
False
True

Example 2: Using a list of 100000 random ints between 1 and 150

// Returns true if x is in range [min..max], else false 
bool inRange(int x, int min=1, int max=100) => ((x - max)*(x - min) <= 0);

// Generate 100000 ints between 1 and 150
var intsToCheck = new List<int>();
var randGen = new Random();
for(int i = 0; i < 100000; ++i){
    intsToCheck.Add(randGen.Next(150) + 1);
}

var counter = 0;
foreach(int n in intsToCheck) {
    if(inRange(n)) ++counter;
}

Console.WriteLine("{0} ints found in range 1..100", counter);

Returns:

66660 ints found in range 1..100

Execution Time: 0.016 second(s)

Answer 10

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

Answer 11

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)').

The only other comment I'd make is that if you're checking inputs with the intention to throw an exception, you should consider using code contracts:

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

This is more elegant than if(...) throw new Exception(...), and you could even get compile-time warnings if someone tries to call your method without ensuring that the number is in bounds first.

Answer 12

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).

Before using an implementation like that, though, benchmark one one's target machine. On some processors, the two-part expression may be faster in all cases since the two comparisons may be done independently whereas in the subtract-and-compare method the subtraction has to complete before the compare can execute.

Answer 13

static class ExtensionMethods
{
    internal static bool IsBetween(this double number,double bound1, double bound2)
    {
        return Math.Min(bound1, bound2) <= number && number <= Math.Max(bound2, bound1);
    }

    internal static bool IsBetween(this int number, double bound1, double bound2)
    {
        return Math.Min(bound1, bound2) <= number && number <= Math.Max(bound2, bound1);
    }
}

Usage

double numberToBeChecked = 7;

var result = numberToBeChecked.IsBetween(100,122);

var result = 5.IsBetween(100,120);

var result = 8.0.IsBetween(1.2,9.6);

Answer 14

These are some Extension methods that can help

  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;
    }

Answer 15

You can use pattern matching to achieve this in the most elegant way:

int i = 5;
if(i is (>0 and <=10))
{

}

Answer 16

Using the built in Range struct (C# 8+), we can create an extension method to check if an Index is within the original range.

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

Since Index overrides the implicit operator, we can pass an int instead of an Index struct.

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

Answer 17

Ok I'll play along. So many answers already but maybe still room for some other novelties:

(obviously don't actually use these)

    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;

OK maybe you could use that last one.

OK one more

    var num = 7;
    const int min = 5;
    const int max = 10;
    var inRange = Enumerable.Range(min, max-min).Contains(num);

Answer 18

If you want to write more code than a simple if, maybe you can: Create a Extension Method called IsBetween

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;
    }

Answer 19

Cause all the other answer are not invented by me, here just my implementation:

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));
        }
    }
}

You can then use it like this:

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

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

Answer 20

I would do a Range object, something like this:

public class Range<T> where T : IComparable
{
    public T InferiorBoundary{get;private set;}
    public T SuperiorBoundary{get;private set;}

    public Range(T inferiorBoundary, T superiorBoundary)
    {
        InferiorBoundary = inferiorBoundary;
        SuperiorBoundary = superiorBoundary;
    }

    public bool IsWithinBoundaries(T value){
        return InferiorBoundary.CompareTo(value) > 0 && SuperiorBoundary.CompareTo(value) < 0;
    }
}

Then you use it this way:

Range<int> myRange = new Range<int>(1,999);
bool isWithinRange = myRange.IsWithinBoundaries(3);

That way you can reuse it for another type.

Answer 21

How about something like this?

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

with the extension method as follows (tested):

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;
    }
}

Answer 22

A new twist on an old favorite:

public bool IsWithinRange(int number, int topOfRange, int bottomOfRange, bool includeBoundaries) {
    if (includeBoundaries)
        return number <= topOfRange && number >= bottomOfRange;
    return number < topOfRange && number > bottomOfRange;
}

Answer 23

When checking if a "Number" is in a range you have to be clear in what you mean, and what does two numbers are equal mean? In general you should wrap all floating point numbers in what is called a 'epsilon ball' this is done by picking some small value and saying if two values are this close they are the same thing.

    private double _epsilon = 10E-9;
    /// <summary>
    /// Checks if the distance between two doubles is within an epsilon.
    /// In general this should be used for determining equality between doubles.
    /// </summary>
    /// <param name="x0">The orgin of intrest</param>
    /// <param name="x"> The point of intrest</param>
    /// <param name="epsilon">The minimum distance between the points</param>
    /// <returns>Returns true iff x  in (x0-epsilon, x0+epsilon)</returns>
    public static bool IsInNeghborhood(double x0, double x, double epsilon) => Abs(x0 - x) < epsilon;

    public static bool AreEqual(double v0, double v1) => IsInNeghborhood(v0, v1, _epsilon);

With these two helpers in place and assuming that if any number can be cast as a double without the required accuracy. All you will need now is an enum and another method

    public enum BoundType
    {
        Open,
        Closed,
        OpenClosed,
        ClosedOpen
    }

The other method follows:

    public static bool InRange(double value, double upperBound, double lowerBound, BoundType bound = BoundType.Open)
    {
        bool inside = value < upperBound && value > lowerBound;
        switch (bound)
        {
            case BoundType.Open:
                return inside;
            case BoundType.Closed:
                return inside || AreEqual(value, upperBound) || AreEqual(value, lowerBound); 
            case BoundType.OpenClosed:
                return inside || AreEqual(value, upperBound);
            case BoundType.ClosedOpen:
                return inside || AreEqual(value, lowerBound);
            default:
                throw new System.NotImplementedException("You forgot to do something");
        }
    }

Now this may be far more than what you wanted, but it keeps you from dealing with rounding all the time and trying to remember if a value has been rounded and to what place. If you need to you can easily extend this to work with any epsilon and to allow your epsilon to change.

Answer 24

Elegant because it doesn't require you to determine which of the two boundary values is greater first. It also contains no branches.

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 );
}

Answer 25

If you are concerned with the comment by @Daap on the accepted answer and can only pass the value once, you could try one of the following

bool TestRangeDistance (int numberToCheck, int bottom, int distance)
{
  return (numberToCheck >= bottom && numberToCheck <= bottom+distance);
}

//var t = TestRangeDistance(10, somelist.Count()-5, 10);

or

bool TestRangeMargin (int numberToCheck, int target, int margin)
{
  return (numberToCheck >= target-margin && numberToCheck <= target+margin);
}

//var t = TestRangeMargin(10, somelist.Count(), 5);

Answer 26

Regarding elegance, the closest thing to the mathematical notation (a <= x <= b) slightly improves readability:

public static bool IsBetween(this int value, int min, int max)
{
    return min <= value && value <= max;
}

For further illustration:

public static bool IsOutside(this int value, int min, int max)
{
    return value < min || max < value;
}

Answer 27

I was looking for an elegant way to do it where the bounds might be switched (ie. not sure which order the values are in).

This will only work on newer versions of C# where the ?: exists

bool ValueWithinBounds(float val, float bounds1, float bounds2)
{
    return bounds1 >= bounds2 ?
      val <= bounds1 && val >= bounds2 : 
      val <= bounds2 && val >= bounds1;
}

Obviously you could change the = signs in there for your purposes. Could get fancy with type casting too. I just needed a float return within bounds (or equal to)

Answer 28

I don't know but i use this method:

    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));
}

And this is the way I can use it:

    [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);
    }

Answer 29

If it's to validate method parameters, none of the solutions throw ArgumentOutOfRangeException and allow easy/proper configuration of inclusive/exclusive min/max values.

Use like this

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

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

I just wrote these beautiful functions. It also has the advantage of having no branching (a single if) for valid values. The hardest part is to craft the proper exception messages.

/// <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);

Answer 30

In C#, the optimal solution with regards to speed and codegen, with only one comparison, no bound checks and not error prone due to overflow is the following:

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

Minimum and maximum value are inclusive.

Answer 31

Using pattern matching can provide 'elegant' code, especially for complex and multiple number range checks. For example:

//complex and multiple range checks
var res = num switch {
   >=11 and <=21 => true, 
   >=43 and <=33 => true,  
   >=67 and <=72 => true,
   _ => false};

//simple one range check, not so elegant!
bool res = num switch { >=11 and <=21 => true, _ => false};

This adds to the answers already provided.

Answer 32

With C# 8 and the new System.Range struct there is one more new option that utilizes the new .. operator and hasn't been mentioned yet.

---

First create an extension for it:

using System;

public static class RangeExtensions
{
    public static bool Contains(this Range range, int value) => range.Start.Value <= value && value < range.End.Value;
}

Then you can apply it to the Range itself:

var isInRange = (1..11).Contains(2);

Answer 33

I use next 'elegant' solution:

using static System.Linq.Enumerable;

int x = 30;
if (Range(1,100).Contains(x))  //true

From Microsoft docs

The using static directive applies to any type that has static members (or nested types), even if it also has instance members. However, instance members can only be invoked through the type instance.

You can access static members of a type without having to qualify the access with the type name:

But this is not trivial for many people, because Enumerable.Range has first argument start and second one count. So this checking may be useful in specific situations, like when you use Enumerable.Range for the foreach loop and before start, you wanted to know, if the loop will be executed.

For example:

        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
        }

Answer 34

You are looking for in [1..100]? That's only Pascal.

Answer 35

June, 2022

int id = 10;
if(Enumerable.Range(1, 100).Select(x => x == id).Any()) // true