AsyncKeyedLock 6.4.2

There is a newer prerelease version of this package available.
See the version list below for details.
dotnet add package AsyncKeyedLock --version 6.4.2                
NuGet\Install-Package AsyncKeyedLock -Version 6.4.2                
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="AsyncKeyedLock" Version="6.4.2" />                
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add AsyncKeyedLock --version 6.4.2                
#r "nuget: AsyncKeyedLock, 6.4.2"                
#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 AsyncKeyedLock as a Cake Addin
#addin nuget:?package=AsyncKeyedLock&version=6.4.2

// Install AsyncKeyedLock as a Cake Tool
#tool nuget:?package=AsyncKeyedLock&version=6.4.2                

AsyncKeyedLock AsyncKeyedLock

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An asynchronous .NET Standard 2.0 library that allows you to lock based on a key (keyed semaphores), limiting concurrent threads sharing the same key to a specified number, with optional pooling for reducing memory allocations.

For example, suppose you were processing financial transactions, but while working on one account you wouldn't want to concurrently process a transaction for the same account. Of course, you could just add a normal lock, but then you can only process one transaction at a time. If you're processing a transaction for account A, you may want to also be processing a separate transaction for account B. That's where AsyncKeyedLock comes in: it allows you to lock but only if the key matches.

The library uses two very different methods for locking, AsyncKeyedLocker which uses an underlying ConcurrentDictionary that's cleaned up after use and StripedAsyncKeyedLocker which uses a technique called striped locking. Both have their advantages and disadvantages, and in order to help you choose you are highly recommended to read about it in the wiki.

A simple non-keyed lock is also available through AsyncNonKeyedLocker.

Installation and usage

Using this library is straightforward. Here's a simple example for using AsyncKeyedLocker:

private static readonly AsyncKeyedLocker<string> _asyncKeyedLocker = new(o =>
    o.PoolSize = 20; // this is NOT a concurrency limit
    o.PoolInitialFill = 1;


using (await _asyncKeyedLocker.LockAsync("test123"))

This libary also supports conditional locking, whether for AsyncKeyedLocker, StripedAsyncKeyedLocker or AsyncNonKeyedLocker. This could provide a workaround for reentrancy in some scenarios for example in recursion:

double factorial = Factorial(number);

public static double Factorial(int number, bool isFirst = true)
  using (await _asyncKeyedLocker.ConditionalLockAsync("test123", isFirst))
    if (number == 0)
      return 1;
    return number * Factorial(number-1, false);

For more help with AsyncKeyedLocker or for examples with StripedAsyncKeyedLocker or AsyncNonKeyedLocker (for simple, non-keyed locking), please take a look at our wiki.


This library has been extensively benchmarked against several other options and our benchmarks run publicly and transparently on Github Actions.


Check out our list of contributors!

Product Compatible and additional computed target framework versions.
.NET net5.0 is compatible.  net5.0-windows was computed.  net6.0 was computed.  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 was computed.  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 is compatible. 
.NET Framework net461 was computed.  net462 was computed.  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 (34)

Showing the top 5 NuGet packages that depend on AsyncKeyedLock:

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Package Description


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Package Description

GitHub repositories (7)

Showing the top 5 popular GitHub repositories that depend on AsyncKeyedLock:

Repository Stars
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Version Downloads Last updated
7.0.0-rc1 89 6/29/2024
7.0.0-beta 78 6/29/2024
7.0.0-alpha 71 6/29/2024
6.4.2 144,519 4/21/2024
6.4.1 936 4/21/2024
6.4.0 335 4/20/2024
6.3.4 544,828 1/23/2024
6.3.4-rc 531 1/23/2024
6.3.4-beta 513 1/23/2024
6.3.3 11,272 1/14/2024
6.3.2 1,009 1/14/2024
6.3.0 1,136 1/14/2024
6.2.6 15,962 1/1/2024
6.2.5 1,206 12/30/2023
6.2.4 52,105 12/6/2023
6.2.3 3,711 12/3/2023
6.2.3-beta 736 12/2/2023
6.2.2 507,590 10/9/2023
6.2.1 1,672,944 4/10/2023
6.2.0 84,974 2/25/2023
6.1.1 60,392 1/27/2023
6.1.1-rc 1,043 1/27/2023
6.1.1-beta 1,047 1/27/2023
6.1.0 16,349 1/26/2023
6.0.5 39,838 1/2/2023
6.0.5-alpha 1,058 12/30/2022
6.0.4 2,358 12/30/2022
6.0.4-rc6 1,042 12/30/2022
6.0.4-rc5 1,073 12/30/2022
6.0.4-rc3 1,048 12/30/2022
6.0.4-rc 1,010 12/29/2022
6.0.4-beta 1,071 12/29/2022
6.0.4-alpha 1,098 12/29/2022
6.0.3 2,850 12/29/2022
6.0.2 27,713 12/18/2022
6.0.1 2,243 12/17/2022
5.1.2 3,313 12/16/2022
5.1.1 10,877 12/13/2022
5.1.0 3,811 12/3/2022
5.0.4 10,425 11/27/2022
5.0.3 2,750 11/26/2022
5.0.3-rc 1,072 11/26/2022
5.0.2-rc 1,026 11/26/2022
5.0.1 3,232 11/19/2022
4.0.2 5,988 11/13/2022
3.2.3 3,595 10/26/2022
3.2.1 2,592 10/23/2022
3.2.0 2,270 10/23/2022
3.0.1 2,778 10/18/2022
3.0.0 2,587 10/16/2022
2.0.3 16,657 6/29/2022
2.0.2 16,754 3/13/2022
2.0.1 2,668 3/13/2022
2.0.0 2,741 3/11/2022
1.1.0 3,900 12/11/2021
1.0.1 2,683 11/22/2021
1.0.0 2,417 11/22/2021

Exposing constructor for AsyncKeyedLockTimeoutReleaser.