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