System.Collections.Immutable 8.0.0

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There is a newer prerelease version of this package available.
See the version list below for details.
dotnet add package System.Collections.Immutable --version 8.0.0
NuGet\Install-Package System.Collections.Immutable -Version 8.0.0
This command is intended to be used within the Package Manager Console in Visual Studio, as it uses the NuGet module's version of Install-Package.
<PackageReference Include="System.Collections.Immutable" Version="8.0.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add System.Collections.Immutable --version 8.0.0
#r "nuget: System.Collections.Immutable, 8.0.0"
#r directive can be used in F# Interactive and Polyglot Notebooks. Copy this into the interactive tool or source code of the script to reference the package.
// Install System.Collections.Immutable as a Cake Addin
#addin nuget:?package=System.Collections.Immutable&version=8.0.0

// Install System.Collections.Immutable as a Cake Tool
#tool nuget:?package=System.Collections.Immutable&version=8.0.0


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.

How to Use

using System.Collections.Immutable;

// Create immutable set of strings
ImmutableHashSet<string> colors = ImmutableHashSet.Create("Red", "Green", "Blue");

// Create a new set by adding and removing items from the original set
ImmutableHashSet<string> colorsModified = colors.Remove("Red").Add("Orange");

foreach (string s in colorsModified)

/* Example output:

Main Types

The main types provided by this library are:

  • System.Collections.Immutable.ImmutableArray
  • System.Collections.Immutable.ImmutableArray<T>
  • System.Collections.Immutable.ImmutableDictionary
  • System.Collections.Immutable.ImmutableDictionary<TKey,TValue>
  • System.Collections.Immutable.ImmutableHashSet
  • System.Collections.Immutable.ImmutableHashSet<T>
  • System.Collections.Immutable.ImmutableList
  • System.Collections.Immutable.ImmutableList<T>
  • System.Collections.Immutable.ImmutableQueue
  • System.Collections.Immutable.ImmutableQueue<T>
  • System.Collections.Immutable.ImmutableSortedDictionary
  • System.Collections.Immutable.ImmutableSortedDictionary<TKey,TValue>
  • System.Collections.Immutable.ImmutableSortedSet
  • System.Collections.Immutable.ImmutableSortedSet<T>
  • System.Collections.Immutable.ImmutableStack
  • System.Collections.Immutable.ImmutableStack<T>
  • System.Collections.Frozen.FrozenDictionary
  • System.Collections.Frozen.FrozenDictionary<TKey, TValue>
  • System.Collections.Frozen.FrozenSet
  • System.Collections.Frozen.FrozenSet<T>

Additional Documentation

Feedback & Contributing

System.Collections.Immutable is released as open source under the MIT license. Bug reports and contributions are welcome at the GitHub repository.

Product Compatible and additional computed target framework versions.
.NET net5.0 was computed.  net5.0-windows was computed.  net6.0 is compatible.  net6.0-android was computed.  net6.0-ios was computed.  net6.0-maccatalyst was computed.  net6.0-macos was computed.  net6.0-tvos was computed.  net6.0-windows was computed.  net7.0 is compatible.  net7.0-android was computed.  net7.0-ios was computed.  net7.0-maccatalyst was computed.  net7.0-macos was computed.  net7.0-tvos was computed.  net7.0-windows was computed.  net8.0 is compatible.  net8.0-android was computed.  net8.0-browser was computed.  net8.0-ios was computed.  net8.0-maccatalyst was computed.  net8.0-macos was computed.  net8.0-tvos was computed.  net8.0-windows was computed. 
.NET Core netcoreapp2.0 was computed.  netcoreapp2.1 was computed.  netcoreapp2.2 was computed.  netcoreapp3.0 was computed.  netcoreapp3.1 was computed. 
.NET Standard netstandard2.0 is compatible.  netstandard2.1 was computed. 
.NET Framework net461 was computed.  net462 is compatible.  net463 was computed.  net47 was computed.  net471 was computed.  net472 was computed.  net48 was computed.  net481 was computed. 
MonoAndroid monoandroid was computed. 
MonoMac monomac was computed. 
MonoTouch monotouch was computed. 
Tizen tizen40 was computed.  tizen60 was computed. 
Xamarin.iOS xamarinios was computed. 
Xamarin.Mac xamarinmac was computed. 
Xamarin.TVOS xamarintvos was computed. 
Xamarin.WatchOS xamarinwatchos was computed. 
Compatible target framework(s)
Included target framework(s) (in package)
Learn more about Target Frameworks and .NET Standard.

NuGet packages (1.9K)

Showing the top 5 NuGet packages that depend on System.Collections.Immutable:

Package Downloads
System.Reflection.Metadata The ID prefix of this package has been reserved for one of the owners of this package by

This package provides a low-level .NET (ECMA-335) metadata reader and writer. It's geared for performance and is the ideal choice for building higher-level libraries that intend to provide their own object model, such as compilers. The metadata format is defined by the ECMA-335 - Common Language Infrastructure (CLI) specification. The System.Reflection.Metadata 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.

Microsoft.CodeAnalysis.Common The ID prefix of this package has been reserved for one of the owners of this package by

A shared package used by the Microsoft .NET Compiler Platform ("Roslyn"). Do not install this package manually, it will be added as a prerequisite by other packages that require it. More details at This package was built from the source at

Microsoft.CodeAnalysis.CSharp The ID prefix of this package has been reserved for one of the owners of this package by

.NET Compiler Platform ("Roslyn") support for C#, Microsoft.CodeAnalysis.CSharp.dll. More details at This package was built from the source at

Humanizer.Core The ID prefix of this package has been reserved for one of the owners of this package by

Humanizer core package that contains the library and the neutral language (English) resources

Npgsql The ID prefix of this package has been reserved for one of the owners of this package by

Npgsql is the open source .NET data provider for PostgreSQL.

GitHub repositories (473)

Showing the top 5 popular GitHub repositories that depend on System.Collections.Immutable:

Repository Stars
.NET Decompiler with support for PDB generation, ReadyToRun, Metadata (&more) - cross-platform!
The Roslyn .NET compiler provides C# and Visual Basic languages with rich code analysis APIs.
.NET is a cross-platform runtime for cloud, mobile, desktop, and IoT apps.
Open Source real-time strategy game engine for early Westwood games such as Command & Conquer: Red Alert written in C# using SDL and OpenGL. Runs on Windows, Linux, *BSD and Mac OS X.
Open-source web application framework for ASP.NET Core! Offers an opinionated architecture to build enterprise software solutions with best practices on top of the .NET. Provides the fundamental infrastructure, cross-cutting-concern implementations, startup templates, application modules, UI themes, tooling and documentation.
Version Downloads Last updated
9.0.0-preview.5.24306.7 730 6/11/2024
9.0.0-preview.4.24266.19 1,169 5/21/2024
9.0.0-preview.3.24172.9 2,494 4/11/2024
9.0.0-preview.2.24128.5 4,284 3/12/2024
9.0.0-preview.1.24080.9 10,001 2/13/2024
8.0.0 14,274,952 11/14/2023
8.0.0-rc.2.23479.6 395,958 10/10/2023
8.0.0-rc.1.23419.4 20,090 9/12/2023
8.0.0-preview.7.23375.6 9,152 8/8/2023
8.0.0-preview.6.23329.7 7,224 7/11/2023
8.0.0-preview.5.23280.8 7,310 6/13/2023
8.0.0-preview.4.23259.5 3,156 5/16/2023
8.0.0-preview.3.23174.8 4,851 4/11/2023
8.0.0-preview.2.23128.3 9,657 3/14/2023
8.0.0-preview.1.23110.8 3,143 2/21/2023
7.0.0 48,595,196 11/7/2022
7.0.0-rc.2.22472.3 53,378 10/11/2022
7.0.0-rc.1.22426.10 15,253 9/14/2022
7.0.0-preview.7.22375.6 6,555 8/9/2022
7.0.0-preview.6.22324.4 6,978 7/12/2022
7.0.0-preview.5.22301.12 1,666 6/14/2022
7.0.0-preview.4.22229.4 14,896 5/10/2022
7.0.0-preview.3.22175.4 110,747 4/13/2022
7.0.0-preview.2.22152.2 83,270 3/14/2022
7.0.0-preview.1.22076.8 63,012 2/17/2022
6.0.0 274,612,462 11/8/2021
6.0.0-rc.2.21480.5 308,550 10/12/2021
6.0.0-rc.1.21451.13 200,916 9/14/2021
6.0.0-preview.7.21377.19 117,325 8/10/2021
6.0.0-preview.6.21352.12 40,222 7/14/2021
6.0.0-preview.5.21301.5 191,304 6/15/2021
6.0.0-preview.4.21253.7 76,337 5/24/2021
6.0.0-preview.3.21201.4 95,514 4/8/2021
6.0.0-preview.2.21154.6 91,362 3/11/2021
6.0.0-preview.1.21102.12 96,962 2/12/2021
5.0.0 284,943,830 11/9/2020
5.0.0-rc.2.20475.5 380,776 10/13/2020
5.0.0-rc.1.20451.14 322,705 9/14/2020
5.0.0-preview.8.20407.11 477,910 8/25/2020
5.0.0-preview.7.20364.11 114,716 7/21/2020
5.0.0-preview.6.20305.6 3,615 6/25/2020
5.0.0-preview.5.20278.1 5,581 6/10/2020
5.0.0-preview.4.20251.6 5,524 5/18/2020
5.0.0-preview.3.20214.6 144,444 4/23/2020
5.0.0-preview.2.20160.6 87,470 4/2/2020
5.0.0-preview.1.20120.5 12,485 3/16/2020
1.7.1 204,265,797 5/12/2020
1.7.0 182,605,453 12/3/2019
1.7.0-preview3.19551.4 187,176 11/13/2019
1.7.0-preview2.19523.17 33,097 11/1/2019
1.7.0-preview1.19504.10 723,556 10/15/2019
1.6.0 34,989,419 9/23/2019
1.6.0-rc1.19456.4 48,891 9/16/2019
1.6.0-preview9.19421.4 1,395,843 9/4/2019
1.6.0-preview9.19416.11 1,251 9/4/2019
1.6.0-preview8.19405.3 386,646 8/13/2019
1.6.0-preview7.19362.9 93,070 7/23/2019
1.6.0-preview6.19303.8 172,262 6/12/2019
1.6.0-preview6.19264.9 1,573 9/4/2019
1.6.0-preview5.19224.8 648,224 5/6/2019
1.6.0-preview4.19212.13 31,214 4/18/2019
1.6.0-preview3.19128.7 210,027 3/6/2019
1.6.0-preview.19073.11 39,269 1/29/2019
1.6.0-preview.18571.3 67,815 12/3/2018
1.5.0 275,952,513 5/29/2018
1.5.0-rc1 361,344 5/6/2018
1.5.0-preview2-26406-04 284,689 4/10/2018
1.5.0-preview1-26216-02 560,306 2/26/2018
1.4.0 136,132,686 8/11/2017
1.4.0-preview2-25405-01 13,869 6/27/2017
1.4.0-preview1-25305-02 17,567 5/9/2017
1.3.1 176,569,818 1/3/2017
1.3.0 223,007,324 11/15/2016
1.3.0-preview1-24530-04 136,315 10/24/2016
1.2.0 303,091,255 6/27/2016
1.2.0-rc2-24027 10,663,690 5/16/2016
1.1.38-beta-23516 36,714 11/18/2015
1.1.38-beta-23409 6,784 10/15/2015
1.1.38-beta-23225 128,553 9/1/2015
1.1.37 6,025,771 7/29/2015
1.1.37-beta-23109 21,995 7/27/2015
1.1.37-beta-23019 6,503 6/30/2015
1.1.36 7,873,134 5/11/2015
1.1.34-rc 32,178 3/6/2015
1.1.33-beta 650,901 12/10/2014
1.1.32-beta 247,001 10/10/2014