NeoSmart.AsyncLock 3.2.1

The ID prefix of this package has been reserved for one of the owners of this package by Prefix Reserved
.NET 5.0 .NET Standard 1.3
dotnet add package NeoSmart.AsyncLock --version 3.2.1
NuGet\Install-Package NeoSmart.AsyncLock -Version 3.2.1
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="NeoSmart.AsyncLock" Version="3.2.1" />
For projects that support PackageReference, copy this XML node into the project file to reference the package.
paket add NeoSmart.AsyncLock --version 3.2.1
#r "nuget: NeoSmart.AsyncLock, 3.2.1"
#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 NeoSmart.AsyncLock as a Cake Addin
#addin nuget:?package=NeoSmart.AsyncLock&version=3.2.1

// Install NeoSmart.AsyncLock as a Cake Tool
#tool nuget:?package=NeoSmart.AsyncLock&version=3.2.1

AsyncLock: An async/await-friendly lock

AsyncLock is an async/await-friendly lock implementation for .NET Standard, making writing code like the snippet below (mostly) possible:

lock (_lockObject)
    await DoSomething();

Unlike most other so-called "async locks" for C#, AsyncLock is actually designed to support the programming paradigm lock encourages, not just the technical elements. You can read more about the pitfalls with other so-called asynchronous locks and the difficulties of creating a reentrance-safe implementation here.

With AsyncLock, you don't have to worry about which thread is running what code in order to determine whether or not your locks will have any effect or if they'll be bypassed completely, you just write code the way you normally would and you'll find AsyncLock to correctly marshal access to protected code segments.

Using AsyncLock

There are only three functions to familiarize yourself with: the AsyncLock() constructor and the two locking variants Lock()/LockAsync() .

AsyncLock() creates a new asynchronous lock. A separate AsyncLock should be used for each "critical operation" you will be performing. (Or you can use a global lock just like some people still insist on using global mutexes and semaphores. We won't judge too harshly.)

Everywhere you would normally use lock (_lockObject) you will now use one of

  • using (_lock.Lock()) or
  • using (await _lock.LockAsync())

That's all there is to it!

Async-friendly locking by design

Much like theSemaphoreSlim class, AsyncLock offers two different "wait" options, a blocking Lock() call and the asynchronous LockAsync() call. The utmost scare should be taken to never call LockAsync() without an await before it, for obvious reasons.

Upon using LockAsync(), AsyncLock will attempt to obtain exclusive access to the lock. Should that not be possible in the current state, it will cede its execution slot and return to the caller, allowing the system to marshal resources efficiently as needed without blocking until the lock becomes available. Once the lock is available, the AsyncLock() call will resume, transferring execution to the protected section of the code.

AsyncLock usage example

private class AsyncLockTest
    var _lock = new AsyncLock();

    void Test()
        // The code below will be run immediately (likely in a new thread)
        Task.Run(async () =>
                 // A first call to LockAsync() will obtain the lock without blocking
                 using (await _lock.LockAsync())
                     // A second call to LockAsync() will be recognized as being
                     // reentrant and permitted to go through without blocking.
                     using (await _lock.LockAsync())
                         // We now exclusively hold the lock for 1 minute
                         await Task.Delay(TimeSpan.FromMinutes(1));

        // This call to obtain the lock is made synchronously from the main thread.
        // It will, however, block until the asynchronous code which obtained the lock
        // above finishes.
        using (_lock.Lock())
            // Now we have obtained exclusive access.
            // <Safely perform non-thread-safe operation safely here>
Product Versions
.NET net5.0 net5.0-windows net6.0 net6.0-android net6.0-ios net6.0-maccatalyst net6.0-macos net6.0-tvos net6.0-windows net7.0 net7.0-android net7.0-ios net7.0-maccatalyst net7.0-macos net7.0-tvos net7.0-windows
.NET Core netcoreapp1.0 netcoreapp1.1 netcoreapp2.0 netcoreapp2.1 netcoreapp2.2 netcoreapp3.0 netcoreapp3.1
.NET Standard netstandard1.3 netstandard1.4 netstandard1.5 netstandard1.6 netstandard2.0 netstandard2.1
.NET Framework net46 net461 net462 net463 net47 net471 net472 net48 net481
MonoAndroid monoandroid
MonoMac monomac
MonoTouch monotouch
Tizen tizen30 tizen40 tizen60
Universal Windows Platform uap uap10.0
Xamarin.iOS xamarinios
Xamarin.Mac xamarinmac
Xamarin.TVOS xamarintvos
Xamarin.WatchOS xamarinwatchos
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Version Downloads Last updated
3.2.1 527,424 1/10/2022
3.2.0 10,322 12/15/2021
3.2.0-preview2 557 10/29/2021
3.2.0-preview1 199 10/18/2021
3.1.0 58,513 4/29/2021
3.1.0-BETA1 301 2/17/2021
3.0.1 27,079 12/18/2020
3.0.0 486 12/15/2020 383,163 5/17/2017 822 5/17/2017
0.3.0 853 5/17/2017
0.2.0 798 5/16/2017
0.1.0 885 5/14/2017

3.2: New TryLock() and TryLockAsync() methods, CancellationToken support for synchronous locking routines.

3.0: Smarter method of detecting recursion for faster and more-reliable locking on all platforms.

3.1: Added synchronous locking that may be intermixed with async locking.

3.2: Added TryLock() and TryLockAsync() methods.