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System.Collections.Immutable package icon

System.Collections.Immutable

This package provides collections that are thread safe and guaranteed to never change their contents, also known as immutable collections. Like strings, any methods that perform modifications will not change the existing instance but instead return a new instance. For efficiency reasons, the implementation uses a sharing mechanism to ensure that newly created instances share as much data as possible with the previous instance while ensuring that operations have a predictable time complexity. The System.Collections.Immutable library is built-in as part of the shared framework in .NET Runtime. The package can be installed when you need to use it in other target frameworks.

Total Downloads
4.1B
4,094,049,099
Published
Jun 9, 2026
Latest stable version

Install

.NET CLI
dotnet add package System.Collections.Immutable --version 10.0.9
Package Manager Console
Install-Package System.Collections.Immutable -Version 10.0.9
PackageReference
<PackageReference Include="System.Collections.Immutable" Version="10.0.9" />

Frameworks

.NETFramework4.6.2 net8.0 net9.0 net10.0 .NETStandard2.0

Dependencies

System.Memory
.NETFramework4.6.2
[4.6.3, )
[6.1.2, )
System.Memory
.NETStandard2.0
[4.6.3, )

Adoption guide

A verified publisher signal is available. Assess fit from the package's supported frameworks, license and dependency graph rather than popularity alone.

Compatibility metadata lists 5 target frameworks; confirm the exact target used by your application.

How to read this guidance

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