InRange

Lightweight C# extension library for checking if an index is within the valid range of arrays and collections. This repository provides extension methods for IEnumerable<T>, ICollection<T>, IList<T>, IQueryable<T>, arrays (including multi-dimensional), and a static helper for index validation.

Project layout

• src/InRangeExtension.cs - core extension methods for index range checking on collections and arrays
• src/InRangeExtension.WithInRange.cs - fluent-style WithInRange extension methods (including multi-dimensional arrays)
• src/InRangeExtension.CheckInRange.cs - CheckInRange extension methods that throw on out-of-range
• tests/ - unit tests (System.InRange.Tests)

Namespace and public types

• Namespace: System.InRange
• Static class: InRangeExtension
• Key methods (overview):
  • bool InRange(this IEnumerable<T> source, int index)
  • bool InRange(this ICollection<T> source, int index)
  • bool InRange(this IList<T> source, int index)
  • bool InRange(this IQueryable<T> source, int index)
  • bool InRange(this T[] source, int index)
  • bool InRange(this T[,] source, int i, int j)
  • bool InRange(this T[,,] source, int i, int j, int k)
  • bool InRange(int index, int? count)
  • TSource WithInRange(..., out bool result) (all above types, including multi-dimensional arrays)
  • void CheckInRange(...); (all above types, throws on out-of-range)

Behavior and features

• Returns true if the index is within [0, source.Count); otherwise, returns false
• Handles null collections gracefully (returns false)
• Supports all major .NET collection interfaces and arrays, including multi-dimensional arrays
• Compatible with a wide range of .NET targets (see below)
• Aggressive inlining for performance on supported platforms
• Performance Note: For IEnumerable<T> and IQueryable<T>, calling Count() will enumerate the entire collection if it does not implement ICollection<T>, IReadOnlyCollection<T>, or similar. For best performance, prefer using overloads for ICollection<T>, IReadOnlyCollection<T>, IList<T>, IReadOnlyList<T>, List<T>, or arrays whenever possible.

Examples

using System.InRange;

var arr = new[] { 10, 20, 30 };
bool valid = arr.InRange(1); // true
bool invalid = arr.InRange(3); // false

IList<string> list = new List<string> { "a", "b" };
bool validList = list.InRange(0); // true

IEnumerable<int> enumerable = new List<int> { 1, 2, 3 };
bool validEnum = enumerable.InRange(2); // true

IQueryable<int> queryable = enumerable.AsQueryable();
bool validQueryable = queryable.InRange(1); // true

// Multi-dimensional arrays
int[,] arr2d = new int[3, 2];
bool valid2d = arr2d.InRange(2, 1); // true
bool invalid2d = arr2d.InRange(3, 0); // false

// Fluent WithInRange usage
arr.WithInRange(1, out var ok1); // returns arr, ok1 == true
arr2d.WithInRange(2, 1, out var ok2d); // returns arr2d, ok2d == true

// Throws if out of range
arr.CheckInRange(1); // ok
// arr.CheckInRange(3); // throws ArgumentOutOfRangeException

bool staticValid = InRangeExtension.InRange(0, 3); // true
bool staticInvalid = InRangeExtension.InRange(3, 3); // false

Supported target frameworks

The project in src/System.InRange.csproj is multi-targeted and aims to be widely compatible. The repository includes support for many targets (examples):

• .NET Standard 1.0 → 2.1
• .NET Framework 3.5 → 4.8.1
• .NET Core 1.0 → 3.1
• .NET 5 → 10

Pick the appropriate target when referencing the library.

Build and test

Requires the .NET SDK. Recommended: .NET 7 or later.

From the repository root:

dotnet restore
dotnet build
dotnet test

License

MIT