C# Range-Foreach Syntax Extensions

Provides the range-foreach syntax for C# 9.0 or higher.

Supported frameworks:

• .NET Framework >= 3.5
• .NET Core >= 1.0
• .NET Standard >= 1.0

Range-Foreach Syntax

Reference source files or the NuGet package to write foreach loops like this:

foreach (var index in 0..100)
{
    // loop body...
}

which is equivalent to the legacy for loop below:

for (int index = 0; index < 100; index++)
{
    // loop body...
}

TIPS: 0 can be omitted in range expressions, e.g. ..100 (equivalent to 0..100).

NOTE: Use ^ to represent negative numbers, e.g. ^100..0 (instead of -100..0).

Stepped Syntax

Use the Step method to write foreach loops like this:

foreach (var index in (99..^1).Step(-2))
{
    // loop body...
}

which is equivalent to the legacy for loop below:

for (int index = 99; index > -1; index -= 2)
{
    // loop body...
}

Dependency Type Polyfill

This syntax requires the System.Range type (and also the System.Index type). Considering that early frameworks do not provide this type, this project includes the polyfill source.

If a third party package that includes the System.Range type (such as IndexRange, etc.) is referenced, define the INDEX_RANGE_EXTERNAL constant in the project file to avoid duplicate definitions:

<DefineConstants>$(DefineConstants);INDEX_RANGE_EXTERNAL</DefineConstants>

Performance Benchmark

BenchmarkDotNet v0.13.10, Windows 11 (10.0.22631.2792/23H2/2023Update/SunValley3)
AMD Ryzen 7 5800H with Radeon Graphics, 1 CPU, 16 logical and 8 physical cores
.NET SDK 8.0.100
  [Host]     : .NET 8.0.0 (8.0.23.53103), X64 RyuJIT AVX2
  DefaultJob : .NET 8.0.0 (8.0.23.53103), X64 RyuJIT AVX2

Method	LoopCount	Mean	StdDev	Ratio	Code Size