AsyncKeyedLock 6.4.0

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See the version list below for details.
dotnet add package AsyncKeyedLock --version 6.4.0
NuGet\Install-Package AsyncKeyedLock -Version 6.4.0
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="AsyncKeyedLock" Version="6.4.0" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add AsyncKeyedLock --version 6.4.0
#r "nuget: AsyncKeyedLock, 6.4.0"
#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 AsyncKeyedLock as a Cake Addin
#addin nuget:?package=AsyncKeyedLock&version=6.4.0

// Install AsyncKeyedLock as a Cake Tool
#tool nuget:?package=AsyncKeyedLock&version=6.4.0

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. 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 (33)

Showing the top 5 NuGet packages that depend on AsyncKeyedLock:

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Volo.Abp.DistributedLocking.Abstractions The ID prefix of this package has been reserved for one of the owners of this package by

Package Description


Entity Framework Core Second Level Caching Library.




Package Description

GitHub repositories (6)

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

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1.0.0 2,275 11/22/2021

New methods for conditional locking which can be used in recursive methods as a workaround for reentrancy. If the condition is false, it enters without locking.