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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
CounterFor 1 0.0037 ns 0.0032 ns ? 20 B
RangeForeach 1 0.0026 ns 0.0010 ns ? 39 B
SteppedRangeForeach 1 0.0051 ns 0.0022 ns ? 39 B
EnumerableRangeForeach 1 7.2937 ns 0.1077 ns ? 593 B
CounterFor 3 0.4622 ns 0.0033 ns 1.00 20 B
RangeForeach 3 0.4623 ns 0.0011 ns 1.00 39 B
SteppedRangeForeach 3 0.4639 ns 0.0034 ns 1.00 39 B
EnumerableRangeForeach 3 9.4142 ns 0.1430 ns 20.37 644 B
CounterFor 10 2.1077 ns 0.0098 ns 1.00 20 B
RangeForeach 10 2.1039 ns 0.0019 ns 1.00 39 B
SteppedRangeForeach 10 2.1064 ns 0.0055 ns 1.00 39 B
EnumerableRangeForeach 10 14.0306 ns 0.0623 ns 6.66 644 B
CounterFor 100 26.3959 ns 0.0289 ns 1.00 20 B
RangeForeach 100 27.8959 ns 0.0137 ns 1.06 39 B
SteppedRangeForeach 100 27.9739 ns 0.0267 ns 1.06 39 B
EnumerableRangeForeach 100 64.2927 ns 0.4154 ns 2.44 644 B
CounterFor 1000 230.8943 ns 0.1496 ns 1.00 20 B
RangeForeach 1000 235.6411 ns 0.1965 ns 1.02 39 B
SteppedRangeForeach 1000 235.9903 ns 0.3364 ns 1.02 39 B
EnumerableRangeForeach 1000 513.7996 ns 1.7926 ns 2.23 644 B