This repository provides implementations (copied from corefx) of System.Index and System.Range for netstandard2.0 and .NET Framework.

This lets you use the new C# 8.0 index and range features in projects that target .NET Framework.

For projects that target netstandard2.0 or .NET Framework 4.6.2 or later, use the Microsoft.Bcl.Memory package instead. This package should be considered deprecated for those target frameworks.

This library is not necessary nor recommended when targeting versions of .NET that include the relevant support.

The package is available on NuGet. To install, run:

dotnet add package IndexRange

The C# compiler needs the RuntimeHelpers.GetSubArray<T> method to be available to create subranges from arrays. This method is only available in netstandard2.1 and .NET Core 3.0, so creating subranges from arrays will fail to compile in .NET Framework.

A workaround is to add a reference to System.Memory and use Span<T>. Not only does this compile, it's much more efficient as it doesn't create a new array and copy the sliced data to it:

int[] array = new[] { 1, 2, 3, 4, 5, 6 };
// don't do this:
// var slice = array[1..^1];
// do this:
var slice = array.AsSpan()[1..^1];

The other fix is to define the necessary method in your source code. Copy the following code into your project:

https://gist.github.com/bgrainger/fb2c18659c2cdfce494c82a8c4803360

That type is not in this NuGet package so that the C# compiler doesn't warn that The predefined type 'RuntimeHelpers' is defined in multiple assemblies.